Sahih al-Bukhari 2835
صحيح البخاري#2835SahihNarrated Anas:The Emigrants and the Ansar started digging the trench around Medina carrying the earth on their backs and saying, "We are those who have given a pledge of allegiance to Muhammad that we will carry on Jihad as long as we live." The Prophet (ﷺ) kept on replying, "O Allah, there is no good except the good of the Hereafter; so confer Your Blessings on the Ansar and the Emigrants
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: 56:51