Prohibiting the Lawful for Oneself and Its Ruling

Question:
He imposed some hardship upon himself. This is based on His saying, “Indeed, this is forbidden for you,” meaning that you come to worship and worship Allah. Abu 'Abd al-'Aziz.

Answer:
One who forbids the lawful falls under the category of oaths. Forbidding the lawful is of two types: forbidding the lawful in the manner of the pre-Islamic age of ignorance, where people used to worship Allah by forbidding what is forbidden. Forbidding the lawful is not permissible; this is an action of the pre-Islamic age, as we recently learned.
The second type is forbidding the lawful in the context of an oath, where one intends to prevent oneself or to bind oneself to something and says, “It is forbidden for me to do such and such if I do not do such and such, or if I do such and such.” This is treated as an oath, and an oath expiation is required for it. This is based on the saying of the Exalted: So Allah called it an oath and commanded its expiation through the oath expiation. The reason was that the Prophet (peace and blessings be upon him), as is reported, forbade honey for himself, or forbade himself from Mariyah the Coptic woman, who was his concubine (peace and blessings be upon him), when some misunderstanding occurred between him and some of his wives. He forbade himself from Mariyah or from honey, so Allah rebuked him: “Why do you forbid what Allah has made lawful for you?” Allah had made it lawful for him, then He commanded him to remove this prohibition through expiation. So this is treated as an oath. Yes.