Assalaamu’ Alaykum. If someone reverts to Islam, and their last name is a family name of people who follow another religion and is known for that, like there are scholars of that religion with that name, should they switch their name. What if this is challenging because of paperwork? Are they allowed to tell others they’re a revert, or is this exposing sin?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

It is not incumbent on a Muslim to change the names of his grandparents and his family name if they do not conform to Sharee‘ah rulings. It was reported in Saheeh Al-Bukhari and Saheeh Muslim in the hadith of Al-Bara’ ibn ‘Azib that the Prophet said during the Battle of Hunayn: “I am the Prophet of Allah and there is no lie about it; I am the son of ‘Abdul-Muttalib.”

Ibn Al-Qayyim  said in Tuhfat Al-Mawdood fi Ahkam Al-Mawlood: “It may be argued that how come the scholars agreed on the prohibition of giving a Muslim child a name that denotes being a slave to other than Allah, The Exalted, although it was authentically reported that the Prophet, said: ‘I am the son of ‘Abdul-Muttalib.’ In refutation, this was not intended to approve the use of this name, rather he was simply informing of the name by which that person (his uncle) was known. Using a name to make known who is being spoken about is not prohibited and saying that this is an exemption for the name of ‘Abd Al-Muttalib, as Abu Muhammad ibn Hazm said, has no basis in the Sharee‘ah, as the Companions also called the tribes of Banu ‘Abd Shams and Banu ‘Abd Ad-Dar by their names, and the Prophet did not forbid it or denounce them for that. Informing of a name is broader than giving a name; what is permissible in the former is not permissible in the latter.”

However, the fact that a family name is commonly used by the adherents of any given religion does not necessitate the prohibition of using it by Muslims, unless it denotes a meaning of which the Sharee‘ah disapproves or it is a name that is specific and exclusive to non-Muslims.

You asked whether it is permissible for that person to inform others that he has converted to Islam and whether he would bear sin for disclosing such information.

It is obviously permissible for a person to tell others that he has become a Muslim without a doubt.

If you are asking whether a person who has not changed his family name is obliged to inform everyone he meets, sees, and hears of his name that he has converted to Islam, it is not obligatory.

If you are asking about the ruling on deliberately concealing one’s conversion to Islam, you should know that if the reason is the person’s inability to proclaim his Islam to ward off real harm, there is nothing wrong with it. However, it is not permissible for this person to proclaim Kufr (disbelief) – by prostrating to idols and invoking other than Allah, The Exalted, for example - except when he is forced to do so. There is a big difference between concealing one’s religion and proclaiming disbelief?

Ibn Taymiyyah said in Minhaj As-Sunnah An-Nabawiyyah: “If a believer lives among non-Muslims and dissolute people, it is not obligatory on him to strive against them with his hand (to forbid the evil of disbelief) despite his inability. If he is able to forbid this evil with his tongue (verbally), he should do so otherwise he is required to forbid it with his heart (by disliking and disapproving of it). However, he may not lie and say what is contrary to what he harbors in his heart. He should either proclaim his religion or conceals it. He may not also approve of their false religion in its totality. What is allowed for him is to do as the believer from the people of Pharaoh and the wife of Pharaoh did. They did not approve of their false religion, but they did not lie and say what was contrary to their beliefs harbored in their hearts. Rather, they concealed their faith.

Concealing one’s religion is one thing, and proclaiming false religion is another. The second was never deemed allowable by Allah, The Exalted, except for the one who is forced to do so. It is allowable for him to utter the words of disbelief under coercion (as a legal concession). Allah, The Exalted, made a distinction between the hypocrite and the believer who is subjected to coercion.”

Allah knows best.