What is the best way in calling to Allah and enjoining good?

Shaykh Abdul Aziz, I have two letters before me: the first is five pages of medium size, and the second is two pages of large size. Both letters are a search for the best way in calling to Allah, and for the best way in enjoining good and forbidding evil:
The first letter is from a sister who has used a pseudonym, saying: "A religious woman." The second letter is from a brother: (A. A. A) from Jeddah. The senders of both letters mention that they observe some errors among Muslims and are greatly pained by what they see. They wish they had the means to change the evil, and they seek guidance. We will dedicate the rest of this session, Your Eminence, if you would be so kind, to the best way in enjoining good and calling to Allah. If you would be so kind, where would you begin?
Answer: Allah has clarified the path of da'wah and what the caller should do. He said : [Yusuf:108]. Therefore, the caller to Allah must have knowledge and insight into what he calls to and what he forbids, so that he does not speak about Allah without knowledge. Sincerity is also obligatory in this, because Allah said: [Yusuf:108]. Not to a madhhab, nor to the opinion of so-and-so or so-and-so, but he calls to Allah, seeking His reward, seeking His forgiveness, seeking the well-being of the people. So it is necessary that it be with sincerity, and it is necessary that it be with knowledge. And He said : [An-Nahl:125]. This is an explanation of the manner of da'wah, and that it is to be done with wisdom, meaning: with knowledge. Allah said, and His Messenger said. Knowledge is called wisdom because it deters from falsehood and aids in establishing the truth. Along with knowledge, there should be good admonition and argument in the best manner when necessary.
For some people, clarifying the truth with its evidence may be sufficient, because they seek the truth, and when it becomes clear to them, they accept it. They may not be in need of admonition. And some people may have some hesitation or some harshness, so they need admonition. So the caller to Allah admonishes, establishes the evidence, and reminds, if necessary, with the harsh, the heedless, and the lax, until they are convinced and until they adhere to the truth.
And the one being called may have some doubt, so he argues about it and wants the doubt to be dispelled. So the caller to Allah clarifies the truth for him with its evidence, and removes the doubt with the evidence of the Shari'ah. But with kind words, good style, and gentleness, not with violence and harshness, so that no doubt remains for the one who is wrong, or for the one being forbidden, or for the one being called. He removes it according to his ability, he removes it with evidence according to his ability. Allah said : [Al-Imran:159]. And Allah said when He sent Musa and Harun to Pharaoh: [Ta-Ha:44]. And he (peace and blessings be upon him) said: And he (peace and blessings be upon him) said: So the caller to Allah must be careful, be gentle, and strive for sincerity to Allah and in treating matters in the way prescribed by Allah: with wisdom, good admonition, and argument in the best manner. And he must be in all of this with knowledge, with insight, and on the right path, until he convinces the seeker of the truth, and until he removes the doubt from the one who has a doubt, and until he softens the hearts of those who have harshness or severity or turning away. He softens the hearts by calling to Allah, good admonition, directing to good, and explaining what he has with Allah of good if he accepts the truth, and what danger he faces if he rejects the truth, among other aspects of admonition.
As for the people of hisbah who enjoin good and forbid evil, it is also obligatory for them to adhere to the Shari'ah etiquettes that the caller to Allah adheres to. So they must be gentle and avoid violence, except when there is a need for it from the oppressors, the arrogant, and the defiant. As for others, it is like what is for the caller: he forbids evil with gentleness and wisdom, and they enjoin good with gentleness and wisdom, and they establish the evidence for it, until the one committing the evil is convinced, and until he is alert, and until he adheres to the truth. And this is according to ability, as he (peace and blessings be upon him) said: Narrated by Muslim. And Allah the Exalted says: [At-Tawbah:71]. And He the Exalted says: [Al-Imran:104]. And He the Exalted says: ([Al-Imran:110]).
And He threatened those who left that and turned away from it, and He cursed them on the tongue of Dawud and Isa ibn Maryam because of their disobedience, their transgression, and their failure to restrain themselves from evil. Where He the Exalted said in His great Book in Surat al-Ma'idah: They were not restraining themselves from an evil they used to do. Evil was what they used to do. [Al-Ma'idah: 78 - 79]. So the matter is great.
So it is obligatory upon the people of faith, and upon the people of capability from the rulers, scholars, and others from the notables of the Muslims who have capability and who have knowledge, to forbid evil and to enjoin good. And this is not specific to a certain group, even though the specific group has its duty and bears the greatest burden. But that does not imply neglecting the others. Rather, it is obligatory for the others to help them and to be with them in forbidding evil and enjoining good, until good increases and evil decreases. Especially if the specific group has not covered what is required and the intended goal has not been achieved, but the matter is wider and the evil is more, then helping them is obligatory in all cases. But if they fulfill what is required and sufficiency is achieved through them, then it is known that this is a collective obligation (fard kifayah). Meaning: enjoining good and forbidding evil is a collective obligation (fard kifayah).
So if the required removal of evil and enjoining of good is achieved by the specific ones or the responsible volunteers, then it becomes a recommended practice (sunnah) for the rest. But as for an evil that has no one to remove it except you, because you are the one present in the village or the tribe or the neighborhood, and there is no one else in it who enjoins good besides you, then it becomes an individual obligation (fard 'ayn) for you to forbid evil and enjoin good, as long as you are the one who knows it and you are the one who can forbid it. Then it is obligatory upon you. So when you find someone else with you, it becomes a collective obligation (fard kifayah). If one of you or you all perform it and the intended goal is achieved, then if you all leave it, you all sin.
So the result is that it is a collective obligation (fard kifayah) for everyone, whenever someone from the society or the tribe or the people of the village or the city performs it who is sufficient, it drops from the rest. And so is calling to Allah. And whenever everyone leaves it, they sin, and the sin becomes general for them, because they fell short of the obligatory duty and did not perform it. And whenever someone performs it who is sufficient in calling, directing, and forbidding evil, it becomes a great recommended practice (sunnah) for the rest, because participation in good is required. Yes.
The presenter: Your Eminence, you emphasize knowledge of the path of calling to Allah, and the path of enjoining good and forbidding evil. Perhaps Your Eminence would specify the knowledge that the one who wants to call to Allah with insight and wants to enjoin good and forbid evil in the Shari'ah way should learn?
The Shaykh: Knowledge is necessary, and knowledge, Allah said and His Messenger said, is that one should care for the Noble Qur'an and the pure Sunnah. He knows what Allah commanded and what Allah forbade. And he knows the way of the Messenger (peace and blessings be upon him) in his calling to Allah and his forbidding of evil, and the way of his Companions (may Allah be pleased with them all). He should be insightful in this, by reviewing the books of the noble hadith, with care for the Noble Qur'an, and by reviewing the words of the scholars in this chapter. May Allah have mercy on them, they expanded the discussion and clarified what is obligatory.
So the one who takes up this matter must care for this matter so that he is on insight from the Book of Allah and the Sunnah of His Messenger (peace and blessings be upon him), so that he places things in their proper places. He places calling to good in its place, and forbidding evil in its place. And so is forbidding evil and enjoining good, it is in its place with insight, with knowledge, so that he does not fall into forbidding evil in a way that is more evil than it, and so that he does not fall into enjoining good in a way that creates more evil than this command he called to.
The point is: that knowledge is necessary so that he places things in their proper places, and so that when he forbids evil, it benefits and does not result in something more evil, and so that when he calls to good, it is hoped that the good is achieved, or at least that no evil results from it that is greater, more significant, and worse than leaving this good. Yes.
The presenter: Our sister, the author of the letter who used the code name "the believing, pious listener," says: If she sees one of her relatives committing some of what is wrong, what should her stance be?
The Shaykh: She has to forbid what is wrong using a good manner, kind words, and gentleness and compassion toward the one committing the wrong; because he may be ignorant, or he may have a harsh temperament, and if he is rebuked severely, his harshness may increase. So she should forbid what is wrong to her sister in Allah and her brother in Allah, but with a good manner, kind words, and mentioning the evidence, saying "Allah said so and so, and His Messenger said so and so," along with supplicating for him for success and guidance. This is how she should possess wisdom, insight, and forbearance, as should the man, so that the one being rebuked accepts what is being forbidden and does not become defiant. That is, the caller should strive, and the one forbidding the wrong should strive to use words through which the acceptance of the truth is hoped for. Yes.
The presenter: If the wrong that this sister sees is free mixing of men and women and not wearing the hijab, how do you advise her, Shaykh Abdul Aziz?
The Shaykh: She should advise them and say to her sister in Allah: "It is obligatory for you to do so and so, to avoid free mixing, it is obligatory for you to avoid being uncovered, to cover yourself from men who are not your mahram (close relatives)." Allah the Exalted said: [Al-Ahzab: 53]. Allah the Exalted said: [An-Nur: 31], the verse. And so she addresses them with verses and texts, [Al-Ahzab: 59]. "O my sister in Allah! The matter is great. Uncovering leads to such and such, and mixing with men leads to such and such. So it is obligatory for us all to beware of what Allah has forbidden, and to cooperate in righteousness and piety, and to enjoin what is right and forbid what is wrong, and to advise one another with truth." And so on... these should be good expressions. Yes.
The presenter: Boycotting the one who commits a sin, O Shaykh Abdul Aziz! What is the caller's stance toward it, especially if it is from among the relatives?
The Shaykh: This requires detail. Boycotting the one who commits what is wrong and severing ties with him requires detail:
It is prescribed to sever ties with him and boycott him if he publicly commits the wrong and persists in it, and advice does not benefit him. It is prescribed for his relative, or his neighbor, or others to sever ties with him, not respond to his invitations, and not greet him, until he repents to Allah from this wrong. This is what the Prophet (peace and blessings be upon him) and the Companions did when Ka'b ibn Malik the Ansari and his two companions lagged behind the Battle of Tabuk without a valid legal excuse. The Prophet (peace and blessings be upon him) ordered that they not be spoken to and that they be boycotted. So they all boycotted him and left him alone; they did not greet him, they did not invite him to a feast, and they did not return his greeting if he greeted them, until they repented, and then Allah accepted their repentance.
However, if severing ties with a person may lead to something even more wrong, because he is a person of status in the state or a person of status in the tribe, then severing ties with him is left, and he is treated with the best manner and shown gentleness, so that severing ties with him does not lead to something worse than his action and uglier than his deed. The evidence for this is that he (peace and blessings be upon him) did not treat Abdullah ibn Abi ibn Salul, the head of the hypocrites, in the same way he treated the three [who lagged behind]. Rather, he was gentle with him and did not boycott him, and he continued to show him gentleness; because he was the leader of his people, and there was fear that killing him, imprisoning him, or boycotting him would cause fitnah (trial/discord) for the community in Medina. For this reason, the Prophet (peace and blessings be upon him) showed him gentleness until he died upon his hypocrisy. We ask Allah for safety.
And here are other instances where it happened to him (peace and blessings be upon him) with some people that he did not boycott them, but rather showed them gentleness, peace and blessings be upon him, until Allah guided them. Yes.
The presenter: So gentleness is what Shaykh Abdul Aziz calls for?
The Shaykh: Yes.
The presenter: May Allah reward you.
The Shaykh: He should boycott if boycoting is better, and he should leave boycoting if leaving it is better, while still forbidding the wrong and showing dislike for the wrong, and that its doer is not a friend or companion, but for such and such reasons, boycoting is left. However, this is done with kind words, wisdom, secret forbidding of the wrong, and advising him through his close ones, so that perhaps he may respond, in addition to other forms of advice and forms of forbidding that reject the wrong.