Narrated `Aisha:

This Verse: "Allah will not punish you for what is unintentional in your oaths." (5.89) was revealed about a man's state men (during his talk), "No, by Allah," and "Yes, by Allah."

حَدَّثَنَا عَلِيُّ بْنُ سَلَمَةَ، حَدَّثَنَا مَالِكُ بْنُ سُعَيْرٍ، حَدَّثَنَا هِشَامٌ، عَنِ أَبِيهِ، عَنْ عَائِشَةَ ـ رضى الله عنها ـ أُنْزِلَتْ هَذِهِ الآيَةُ ‏{‏لاَ يُؤَاخِذُكُمُ اللَّهُ بِاللَّغْوِ فِي أَيْمَانِكُمْ‏}‏ فِي قَوْلِ الرَّجُلِ لاَ وَاللَّهِ، وَبَلَى وَاللَّهِ‏.‏
USC-MSA web (English) reference : Vol. 6, Book 60, Hadith 137
Arabic reference : Book 65, Hadith 4613