Sahih al-Bukhari 412
صحيح البخاري#412SahihNarrated Anas:The Prophet (ﷺ) said, "None of you should spit in front or on his right but he could spit either on his left or under his foot
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: 8:62