Verse 225

لَّا يُؤَاخِذُكُمُ ٱللَّهُ بِٱللَّغْوِ فِىٓ أَيْمَـٰنِكُمْ وَلَـٰكِن يُؤَاخِذُكُم بِمَا كَسَبَتْ قُلُوبُكُمْ وَٱللَّهُ غَفُورٌ حَلِيمٌ

God does not hold you responsible for your casual oaths, however, He holds you responsible for your actual intentions in your hearts. And God is All Forgiving, Clement.