If someone does something against his oath due to forgetfulness
حَدَّثَنِي يُوسُفُ بْنُ مُوسَى، حَدَّثَنَا أَبُو أُسَامَةَ، قَالَ حَدَّثَنِي عَوْفٌ، عَنْ خِلاَسٍ، وَمُحَمَّدٍ، عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم " مَنْ أَكَلَ نَاسِيًا وَهْوَ صَائِمٌ فَلْيُتِمَّ صَوْمَهُ، فَإِنَّمَا أَطْعَمَهُ اللَّهُ وَسَقَاهُ ".
Narrated Abu Huraira: The Prophet (ﷺ) said, "If somebody eats something forgetfully while he is fasting, then he should complete his fast, for Allah has made him eat and drink."