Al-Ma'idah 5:89 لا يواخذكم الله باللغو في ايمانكم ولاكن يواخذكم بما عقدتم الايمان فكفارته اطعام عشرة مساكين من اوسط ما تطعمون اهليكم او كسوتهم او تحرير رقبة فمن لم يجد فصيام ثلاثة ايام ذالك كفارة ايمانكم اذا حلفتم واحفظوا ايمانكم كذالك يبين الله لكم اياته لعلكم تشكرون ٨٩

Allâh will not punish you for what is unintentional in your oaths, but He will punish you for your deliberate oaths; for its expiation feed ten Masâkîn (poor persons), on a scale of the average of that with which you feed your own families, or clothe them or manumit a slave. But whosoever cannot afford (that), then he should fast for three days. That is the expiation for the oaths when you have sworn¹. And protect your oaths (i.e. do not swear much)². Thus Allâh make clear to you His Ayât (proofs, evidence, verses, lessons, signs, revelations, etc.) that you may be grateful.