In the Sahih, on the authority of Aishah (may Allah be pleased with her), the Messenger of Allah (blessings and peace be upon him) said, “Whoever vows to obey Allah must obey Him, and whoever vows to disobey Allah must not disobey Him.” (1)

Aishah: the Mother of the Believers, wife of the Prophet (blessings and peace be upon him) and daughter of Abu Bakr al-Siddiq (may Allah be pleased with them both). She was the most knowledgeable of all women and the best of the Prophet’s wives after Khadijah—though scholars differ over which of the two has greater merit. She died in 57 AH.

in the Sahih: i.e., Sahih al-Bukhari.

must obey Him: meaning he is to carry out the act of obedience he vowed to perform.

must not disobey Him: meaning he is not to carry out the act of disobedience he vowed to perform.

Overall meaning of the hadith: The Prophet (blessings and peace be upon him) commands anyone who has made a vow of obedience—such as offering extra prayers, giving charity, and the like—to fulfill that vow. He forbids anyone who has made a vow involving sin from carrying it out—such as vowing to offer a sacrifice to other than Allah, to pray at graves, to travel for the purpose of visiting them, and other acts of disobedience.

Relevance of the hadith to this chapter: it shows that a vow can be an act of obedience or an act of sin; hence a vow itself is worship. Accordingly, whoever makes a vow to other than Allah has committed shirk by directing worship to someone else.

Points derived from the hadith:
1 – A vow is worship; offering it to anyone other than Allah is shirk.
2 – It is obligatory to fulfill a vow of obedience.
3 – It is forbidden to fulfill a vow that entails sin.