Sahih Bukhari, Chapter: Jihaad (Fighting for the cause of Allah)

The Muhajirun (Emigrants) and the Ansar started digging the trench around Medina carrying the earth on their backs and saying, "We are those who have given the baia (pledge of allegiance) to Muhammad that we will I carry on Jihad as long as we live." The Prophet (SAW) kept on replying, "O Allah, there is no good except the good of the Hereafter; so confer Your Blessings on the Ansar and the Muhajirun."