Sayyiduna Anas bin Malik (may Allah be pleased with him) said: Once, on a cold morning, the Prophet (peace and blessings be upon him) went out to the Muhajirun and the Ansar, who were digging the trench. He (peace and blessings be upon him) said: "O Allah, the true good is the good of the Hereafter, so forgive the Ansar and the Muhajirun." They replied: "We are those who have pledged to Muhammad (peace and blessings be upon him) that we will keep striving in jihad as long as we live."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13292