Ibn ‘Umar (may Allah be pleased with him) reported:
The Prophet (may Allah's peace and blessings be upon him) forbade vowing and said: "Indeed, it does not bring any good; rather it is only a means to extract something from the miser."
Reported by Muslim (No. 1639c, 1639d), An-Nasa’i (No. 3801) and Ahmad (No. 5335).
The Prophet (may Allah's peace and blessings be upon him) forbade making a vow, which means that a person obliges himself to do something not ordained upon him by the Shariah. He said: A vow does not advance anything or postpone it. Rather. it is only a means whereby something can be extracted from the miser who only does what is obligatory for him; and a vow does not bring about something that had not been predestined for him.
Lessons
It is not prescribed in the Shariah to make a vow, but if a person makes one, he is obligated to fulfill it, unless it involves a sin.
The cause for the forbiddance is that "it does not bring good", as it cannot ward off anything decreed by Allah, and lest a vow maker may think that the fulfillment of his need was the result of the vow. Allah Almighty is Free of need for that.
Al-Qurtubi said: This forbiddance lies where one may say, for example: If Allah cures my sick person, I shall give such and such in charity. The reason behind dislike is that when he made the mentioned act of piety dependent upon the mentioned purpose, it appeared that he did not have the intention to draw close to Allah Almighty for what He did, but he took the path of compensation in this regard. This is made clear by the fact that if He did not cure his sick person, he would not give the charity he made conditional upon this cure. Such is the attitude of a miser, who does not give anything of his money without immediate compensation that is mostly higher than the given amount.
Explanation in Arabic
نَهَى صلى الله عليه وسلم عن النذر، وهو أنْ يُوجِبَ الإنسان على نفسه شيئًا لم يُلزِمْه به الشَّارعُ، وقال: بأنّ النذر لا يقدِّم شيئًا ولا يؤخِّره، وإنما يُستخرج به من البخيل الذي لا يفعل إلا الواجب عليه، وأنَّ النذر لا يأتي بشيء لم يكن قد قدِّر له.
لا يُشرع النذر، لكن إذا نَذَرَ وَجَب عليه الوفاء به إن لم يكن معصية.
العلة في النهي (أنه لا يأتي بخير)؛ لأنه لا يَردُّ من قضاء الله شيئًا؛ ولئلا يَظن الناذِر أن حصول طلبه كان بسبب النذر، والله تعالى غني عن ذلك.
قال القرطبي: هذا النهي محلُّه أن يقول مثلًا: إن شفى الله مريضي فعليَّ صدقة كذا، ووجه الكراهة أنه لما وقَف فِعْلَ القُربة المذكور على حصول الغرض المذكور، ظهر أنه لم يَتَمَخَّض له نية التقرُّب إلى الله تعالى لِما صَدَر منه بل سلك فيها مسلك المعاوضة، ويوضِّحه أنه لو لم يشفِ مريضه لم يتصدّق بما علَّقه على شفائه، وهذه حالة البخيل، فإنه لا يُخرج من ماله شيئًا إلا بعوضٍ عاجل يزيد على ما أخرج غالبًا.
