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."  

عَنْ عَائِشَةَ ؓ أُنْزِلَتْ هَذِهِ الآيَةُ {لاَ يُؤَاخِذُكُمُ اللَّهُ بِاللَّغْوِ فِي أَيْمَانِكُمْ} فِي قَوْلِ الرَّجُلِ لاَ وَاللَّهِ وَبَلَى وَاللَّهِ  

regarding: 'Allah will not call you to account for that which is unintentional in your oaths...' (2.225) This Verse was revealed concerning such oath formulas as: 'No, by Allah!' and 'Yes, by Allah!' something against his oath due to forgetfulness should he make expiation?). And the Statement of Allah: 'And there is no blame on you if you make a mistake therein.' (33.5) And Allah said:-- '(Moses said to Khadir): Call me not to account for what I forgot.' (18.73)  

عَنْ عَائِشَةَ ؓ {لاَ يُؤَاخِذُكُمُ اللَّهُ بِاللَّغْوِ} قَالَ قَالَتْ أُنْزِلَتْ فِي قَوْلِهِ لاَ وَاللَّهِ بَلَى وَاللَّهِ