Amr bin Shu'ayb narrates from his father, and he from his grandfather (may Allah be pleased with him), that the wife of Abu Dharr (may Allah be pleased with him) came riding al-Qaswa', the she-camel, and it was made to kneel near the mosque. She said: O Messenger of Allah! I vowed that if Allah saved me, I would eat of its liver and the meat of its hump. He (peace and blessings be upon him) said: "You have repaid it badly." He said: "This is not a vow. A vow is only that by which the pleasure of Allah is sought."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النذور / 20091