The Requirement of Knowledge for the Caller to Allah

Question:
This is a questioner who has used the code name "Your Brother (M. K)" who says: O Shaykh! What are the conditions that must be present in a caller to Allah if he wants to call to Allah ? And does a person call with the minimum amount of knowledge, or is it obligatory for him to learn some of the Islamic legal sciences? And what are these sciences, O Shaykh? May Allah reward you.

The Shaykh:
In the name of Allah, the Most Gracious, the Most Merciful. Praise be to Allah, and may Allah send blessings and peace upon the Messenger of Allah, and upon his family and his Companions, and upon those who follow his guidance.
As for what follows:
The caller to Allah must have clear insight; because Allah, Exalted and Majestic, says: [Yusuf: 108]. He must have knowledge; he must have knowledge of the great Qur'an and the pure Sunnah. If he has knowledge and insight from the Qur'anic evidence and the Prophetic evidence from the Messenger (peace and blessings be upon him), then he calls to Allah according to his knowledge, whether he is a graduate of the colleges of Shari'ah, or colleges of Da'wah, or colleges of Hadith, or colleges of the Qur'an, or has studied in the mosques under the scholars.
The point is: if he has knowledge of the Qur'an and the Sunnah, he calls to Allah, teaches people their religion, guides them to the oneness of Allah and His worship, teaches them what Allah has made obligatory upon them, warns them of what Allah has forbidden, and encourages and instills fear as Allah has prescribed. And if he does not have knowledge, it is not permissible for him to speak about what he does not know. But if a person has knowledge of some matters, he calls to them, just as a believer calls his brothers to prayer even if he is a layman; because prayer is a known matter. He calls them to prayer and to maintaining it in congregation. He calls them to dutifulness to parents; this is a known matter. He calls them to paying zakah; this is a known matter. He calls them to fasting Ramadan; this is a known matter. Even if the layman strives with his family and his brothers to care for these matters. Likewise, he warns against zina... against doubtful matters... against riba... against undutifulness to parents... against drinking intoxicants. These are known matters. But the things that may be hidden require knowledge, so one does not speak about them except the one who has knowledge.
As for the clear, well-known matters of the religion by necessity, the scholar and the non-scholar speak about them. So a person, with his family and his neighbors, advises them in the apparent matters: warning them from what Allah has forbidden, encouraging the performance of prayer in congregation... encouraging dutifulness to parents in maintaining family ties. These are known matters, praise be to Allah.
But it is not permissible for the caller to Allah to speak about what he does not know. Rather, he must seek out what the Qur'an and the Sunnah indicate; so that he is on clear insight in his calling, as Allah, the Exalted, said: [Yusuf: 108]. And Allah, Exalted and Majestic, says: [Al-A'raf: 33]. He placed speaking without knowledge at the peak, above shirk, because of the greatness of its danger. And He, the Exalted, informed that Shaytan commands that, so He said about Shaytan: [Al-Baqarah: 169].
So Shaytan calls people to speak without knowledge and to call with ignorance, and this is a great abomination. Rather, the caller to Allah must verify and must learn so that he is on clear certainty and insight regarding what he calls to and what he forbids. But the apparent, well-known matters of the religion by necessity, the scholar and the non-scholar call to them, as mentioned before, such as warning from zina... warning from undutifulness... warning from severing family ties... warning from riba. This is a known matter. Likewise, he calls to prayer in congregation... he calls his brothers, his neighbors, and his family, and warns them from backbiting and talebearing. All these are known matters. Yes.

The presenter: May Allah reward you and bless you, O Shaykh.