From Sahih Bukhari (Hadith 2835):
Narrated 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
Reference: Bukhari 2835