عَن عِمْرَانَ بْنِ حُصَيْنٍ
قَالَ: سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ: «النَّذْرُ نَذْرَانِ: فَمَنْ كَانَ نَذَرَ فِي طَاعَةٍ فَذَلِكَ لِلَّهِ فِيهِ الْوَفَاءُ وَمَنْ كَانَ نَذَرَ فِي مَعْصِيَةٍ فَذَلِكَ لِلشَّيْطَانِ وَلَا وَفَاء فِيهِ وَيُكَفِّرُهُ مَا يُكَفِّرُ الْيَمِينَ»
Imran ibn Husayn told that he heard God’s Messenger say, “Vows are of two kinds, so if anyone vows to do an act of obedience, that is for God and must be fulfilled; but if anyone vows, to do an act of disobedience, that is for the devil and must not be fulfilled, but he must make atonement for it to the extent he would do in the case of an oath.”
Mishkat al-Masabih 3310, Book 16, Oaths and Vows, Hadith 38. 1 min read