What is the legal basis for the validity of vows (Nadhar)?

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The legal basis for vows rests upon the Book (Quran), the Sunnah, and scholarly consensus (Ijma). Evidence from the Quran includes the verses where Allah states, "They fulfill their vows" (Quran 76:7) and "and let them fulfill their obligations" (Quran 22:29). From the Sunnah, it is related that the Prophet, peace be upon him, said, "Whoever vows to obey Allah, let him obey Him, and whoever vows to disobey Allah, let him not disobey Him." Furthermore, Muslims have reached a consensus on the general validity of vows and the obligation to fulfill them.