Sahih al-Bukhari, Book 11, Hadith 22 (In-Book) ⓘ
Narrated Abu Huraira through different narrators that the Prophet said, "It is Allah's right on every Muslim that he should take a bath (at least) once in seven days."
رَوَاهُ أَبَانُ بْنُ صَالِحٍ عَنْ مُجَاهِدٍ، عَنْ طَاوُسٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم " لِلَّهِ تَعَالَى عَلَى كُلِّ مُسْلِمٍ حَقٌّ أَنْ يَغْتَسِلَ فِي كُلِّ سَبْعَةِ أَيَّامٍ يَوْمًا " .
also referenced under: Hadith 898 (DarusSalam) & Volume 2, Book 13, Hadith 21 (USC-MSA)