Sahih al-Bukhari 897
صحيح البخاري#897SahihNarrated Abu Huraira: Allah's Messenger (ﷺ) said "We are the last (to come amongst the nations) but (will be) the foremost on the Day of Resurrection. They were given the Holy Scripture before us and we were given the Quran after them. And this was the day (Friday) about which they differed and Allah gave us the guidance (for that). So tomorrow (i.e. Saturday) is the Jews' (day), and the day after tomorrow (i.e. Sunday) is the Christians'." The Prophet (ﷺ) remained silent (for a while) and then said, "It is obligatory for every Muslim that he should take a bath once in seven days, when he should wash his head and body
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 11:21