"A vow is like an oath, its expiation is the expiation of an oath." It was recorded by Aḥmad (4/149 and 156) through the route of Ibn Lahīʿah who said: Kaʿb ibn ʿAlqamah narrated to us, saying: I heard ʿAbd al-Raḥmān ibn Shamāsah say: We came to Abū al-Khayr, and he said: I heard ʿUqbah ibn ʿĀmir say: I heard the Messenger of Allāh (ṣallá Allāhu ʿalayhi wa-sallam) say it, and he mentioned it. I said: Its narrators are reliable except for Ibn Lahīʿah, who had poor memory, but I found that Shaykh al-Islām Ibn Taymiyyah (may Allāh have mercy on him) definitively attributed it to the Prophet (ṣallá Allāhu ʿalayhi wa-sallam), using it as evidence that every vow is an oath. He said in "al-Fatāwá" (3/358): "The evidence for this is the saying of the Prophet (ṣallá Allāhu ʿalayhi wa-sallam): the vow is an oath." If Shaykh al-Islām found another route for the ḥadīth, then it is strong; otherwise, it is not. The first possibility is more likely because the wording he narrated is different from this, and Allāh knows best. Yes, the ḥadīth came in Ṣaḥīḥ Muslim and others from ʿUqbah in a shortened form with the wording: "The expiation of a vow is the expiation of an oath," which is a strong witness for the ḥadīth, and it is referenced in "Irwāʾ al-Ghalīl" (2586). Then I saw the ḥadīth in "Muʿjam al-Ṭabarānī al-Kabīr" (17/313/866) and "Musnad al-Rūyānī" (Q 54/1) through the route of Ibn Lahīʿah also, with wording close to that of Ibn Taymiyyah: "The vow is an oath, and its expiation is the expiation of an oath." However, he said: (Ibn Shamāsah from ʿUqbah), without mentioning (Abū al-Khayr) between them. It is likely from Ibn Lahīʿah, as they criticized him for his memory, and the more likely view is to affirm it, as mentioned in Aḥmad's narration. I found a strong corroborator for him, as al-Ṭaḥāwī said in "Sharḥ al-Maʿānī" (2/74-75): Yūnus narrated to us, saying: Ibn Wahb narrated to us, saying: ʿAmr ibn al-Ḥārith informed me about..