The ruling on one who says: “I will become a Jew or a Christian if I do such-and-such”

Question:
What is the ruling on one who says: “I will become a Jew or a Christian if I do such-and-such” and then does it, or “It is forbidden for me if I do not do such-and-such” and then does not do it?

Answer:
It is not permissible for him to make such a statement; it is not permissible. The Messenger (peace and blessings be upon him) prohibited this. The Messenger (peace and blessings be upon him) said: . It is also not permissible to forbid what Allah has made lawful. Allah the Mighty and Majestic says: [Al-Tahrim: 1]. Therefore, it is not permissible for a person to forbid what Allah has made lawful for him. One must be cautious of this. If he says, “It is forbidden for me to do this,” or “It is forbidden for me to speak such-and-such words,” then he owes an oath expiation, as Allah the Mighty and Majestic said: [Al-Tahrim: 1-2]. If he says, “It is forbidden for me to speak to so-and-so,” or “It is forbidden for me to eat so-and-so’s food,” or “It is forbidden for me to visit so-and-so,” and then he breaks his word, he owes an oath expiation. Its ruling is the ruling of an oath.
He also asks: If he says, “I swear upon you that you will do such-and-such,” is that an oath? And is his saying “By Allah’s life” or “By the life of Allah” or “By Allah” an oath?
The Shaykh: “By my life” or “By your life” is not an oath. And “I swear upon you” is not an oath unless he specifies, saying “I swear upon you by Allah,” or he says “By Allah,” or “By Allah’s life,” or “By Allah.” As for “By Allah’s life,” that is an oath. If he says, “By Allah’s life, I will do such-and-such,” this is an oath, as he (peace and blessings be upon him) said: and . “By Allah’s life” is an oath.