لاَ يُؤَاخِذُكُمُ اللّهُ بِاللَّغْوِ فِي أَيْمَانِكُمْ وَلَكِن يُؤَاخِذُكُم بِمَا عَقَّدتُّمُ الأَيْمَانَ فَكَفَّارَتُهُ إِطْعَامُ عَشَرَةِ مَسَاكِينَ مِنْ أَوْسَطِ مَا تُطْعِمُونَ أَهْلِيكُمْ أَوْ كِسْوَتُهُمْ أَوْ تَحْرِيرُ رَقَبَةٍ فَمَن لَّمْ يَجِدْ فَصِيَامُ ثَلاَثَةِ أَيَّامٍ ذَلِكَ كَفَّارَةُ أَيْمَانِكُمْ إِذَا حَلَفْتُمْ وَاحْفَظُواْ أَيْمَانَكُمْ كَذَلِكَ يُبَيِّنُ اللّهُ لَكُمْ آيَاتِهِ لَعَلَّكُمْ تَشْكُرُونَ
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سورة المائدة
(5/89) Allah does not call you to account for what is vain in your oaths. But He calls you to account for the making of deliberate oaths. So its expiation is the feeding of ten needy out of the middling you feed your families with, or their clothing, or the freeing of a slave. But whosoever cannot find these, should fast for three days. This is the expiation of your oaths when you break them (your oath). And guard your oaths. Thus does Allah make clear to you His Verses, that you may be grateful.
Surah Al-Ma'idah