Hazrat Anas (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) went out early in the morning while the Muhajireen and Ansar were digging the trench. When he (peace and blessings be upon him) looked towards them, he recited this verse: "Beware! The real life is the life of the Hereafter. O Allah! Forgive the Ansar and the Muhajireen." In response, the companions (may Allah be pleased with them) recited this verse: "We are those who have pledged allegiance to Muhammad (peace be upon him), to engage in jihad as long as we remain."