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Surah 5. Al-Ma'ida
Ayah 89
٨٩. لَا يُؤَاخِذُكُمُ ٱللَّهُ بِٱللَّغْوِ فِىٓ أَيْمَـٰنِكُمْ وَلَـٰكِن يُؤَاخِذُكُم بِمَا عَقَّدتُّمُ ٱلْأَيْمَـٰنَ ۖ فَكَفَّـٰرَتُهُۥٓ إِطْعَامُ عَشَرَةِ مَسَـٰكِينَ مِنْ أَوْسَطِ مَا تُطْعِمُونَ أَهْلِيكُمْ أَوْ كِسْوَتُهُمْ أَوْ تَحْرِيرُ رَقَبَةٍ ۖ فَمَن لَّمْ يَجِدْ فَصِيَامُ ثَلَـٰثَةِ أَيَّامٍ ۚ ذَٰلِكَ كَفَّـٰرَةُ أَيْمَـٰنِكُمْ إِذَا حَلَفْتُمْ ۚ وَٱحْفَظُوٓا۟ أَيْمَـٰنَكُمْ ۚ كَذَٰلِكَ يُبَيِّنُ ٱللَّهُ لَكُمْ ءَايَـٰتِهِۦ لَعَلَّكُمْ تَشْكُرُونَ
[89] Allah does not take you to task for the inadvertent oaths you swear, but He will surely call you to account for the intentional and deliberate oaths you make. The expiation (of breaking such an oath) is to feed ten indigent persons with the normal food you serve in your own family, or to give them clothes, or to free one slave, and the one who cannot afford any of these let him fast three days. This is the expiation of breaking the solemn oaths you have taken;106 be mindful of your oaths.107 Thus Allah makes His Commandments plain to you so that you may show gratitude.
106The Commandment about oaths has been laid down here in connection with instructions about food, because some people had taken oaths of making some lawful things unlawful for themselves. The Commandment is that if one uttered a word of oath without any Intention behind it, one shall not be bound to observe it, for there is no punishment or expiation for this. But if one has deliberately taken such an oath, one must break it and expiate the violation because one must abrogate such a sinful oath. (Please also refer to E.N.'s 243 and 244 of Al-Baqarah and E.N. 125 of An-Nisa).
107"Being mindful of an oath'' implies three things. First, one should make the right use of an oath and should not take it for useless and sinful things. Secondly, when one takes an oath for anything, one should remember it lest one should forget' it and violate it. Thirdly, if one takes a deliberate oath to do aright thing, one must fulfill it, and if one violates it, one should expiate the sin.