What are the classifications of oaths?
General Chapter
Al-Mughni
Book of Oaths
Primary text
Oaths are divided into five categories. The first category is obligatory (Wajib), such as when an oath is required to save a life from peril, like swearing that a captive is one's brother to secure his release, as this aligns with the obligation to save a Muslim life. It is also obligatory to save oneself, such as when facing the Qasamah oaths (oaths of accusation in homicide cases) while being innocent. The second category is recommended (Mandub), which pertains to oaths that lead to an interest, such as reconciling disputants, removing hatred from a Muslim's heart, or averting harm. Oaths promising to perform an act of obedience or refrain from disobedience are subject to two views: one holding them recommended as they encourage good conduct, and another holding they are not recommended, as the Prophet and his Companions rarely did this, and it resembles a vow, which the Prophet prohibited.
Supporting text
The third category is permissible (Mubah), which includes swearing to do or leave an indifferent matter, or swearing to a known truth or a perceived truth. God Almighty stated that He does not hold one accountable for idle oaths, which includes swearing to something believed true at the time but later found otherwise. The fourth category is detested (Makruh), which involves swearing to perform a detested act or abandon a recommended one, such as swearing not to spend on relatives or swearing in buying and selling, as the Prophet said, "Swearing expedites the sale but effaces the blessing."