The Ruling on Shaking Hands with a Non-Mahram Woman to Encourage Her in Calling to Allah

Question:
After Allah granted me the blessing of tawhid (the oneness of Allah) in this land during the last three years, and by the permission of Allah, after I have taken my share of beneficial knowledge in the sciences of tawhid and other forms of worship; I found that travel is near—if Allah wills—to my homeland and my place of origin. As is the custom of the people of the region and the country, there are my parents, my siblings, my cousins, and my aunts to welcome me. It is my intention, after arriving at my relatives there, to engage in calling to tawhid among my close relatives specifically, and the people of the region generally. Is it permissible for me to shake hands with these close female relatives, such as my cousins and aunts, when they welcome me, given that they are all ignorant of the correct tawhid? Or should I not shake hands with them, despite their ignorance of tawhid? I fear they may refuse to accept this call, even though it is the foundation of the religion.

Answer:
It is obligatory for the student of knowledge to exert what knowledge he has, and to call to Allah in the lands that need it, where no one else is in a position to take his place. He should strive for gentleness, kindness, good speech, and a good manner in conveying the call. If the people of his land are ignorant of some of the rulings of Allah, he should present them to them, explain the rulings of Allah to them, and guide them. Even if some of them have something in their hearts, customs that contradict the Shari'ah are not permissible to respect. Were the messengers ever opposed except by customs that contradicted the truth? The messengers were not opposed except by customs that contradicted the truth, so patience is necessary.
If that is the case, then approach them before that. Write to them now, before you go to them. Write to them and say to them: It is the custom of our country to do such and such, and I advise you to leave that and not do it; so that they know that while you are in the country before you travel to them. And when you arrive at them, say to them before greeting them: "O my sisters, O my cousins, O such and such, O such and such," you say to them: I have learned and known that this is not permissible, and the greeting is done without shaking hands, this is with cousins, maternal aunts, and the like.
As for your sisters, aunts, and maternal aunts, there is no harm. This is only with non-mahrams: such as a cousin, a maternal cousin, a daughter of a maternal aunt, and neighbors. You greet them, but without shaking hands. How are you? How are your children? You greet them, welcome them, and ask about their conditions, but without shaking hands.
It is established from him (peace and blessings be upon him) that he said: When some women extended their hands to him, he said: despite what Allah gave him of faith, wisdom, and protection—(peace and blessings be upon him)—and Aisha (may Allah be pleased with her) said: "By Allah, the hand of the Messenger of Allah (peace and blessings be upon him) never touched the hand of a woman. He did not take their pledge except with words—(peace and blessings be upon him)."

The intended meaning : That the believer should emulate the Prophet (peace and blessings be upon him) and not seek the pleasure of people for another matter. Allah guides whom He wills and misguides whom He wills. It is upon you to know what is upon you: if they are guided, then for them and for you is the reward; and if they refuse, then you have fulfilled what is upon you. It is only upon you to convey the message, as was the practice of the messengers (peace and blessings be upon them).