Narrated 'Aishah (RA):

Allah's Messenger (ﷺ) swore that he would stay away from his wives for a period. He made something unlawful (for himself) (i.e. something not in itself unlawful). So, he made the lawful unlawful, and he made atonement for breaking an oath. [Reported by at-Tirmidhi, and its narrators are reliable (thiqah)].

عَنْ عَائِشَةَ رَضِيَ اَللَّهُ عَنْهَا قَالَتْ: { آلَى رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-مِنْ نِسَائِهِ وَحَرَّمَ, فَجَعَلَ اَلْحَرَامَ حَلَالًا , وَجَعَلَ لِلْيَمِينِ كَفَّارَةً.‏ } رَوَاهُ اَلتِّرْمِذِيُّ, وَرُوَاتُهُ ثِقَاتٌ .‏ [1]‏ .‏