Sahih al-Bukhari 7202
صحيح البخاري#7202SahihNarrated `Abdullah bin `Umar:Whenever we gave the Pledge of allegiance to Allah's Messenger (ﷺ) for to listen to and obey, he used to say to us, for as much as you can
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: 93:62