Sahih Bukhari | Volume 9 | Hadith Number 308

Narrated by Anas
The Prophet went out on a cold morning while the Muhajirin (emigrants) and the Ansar were digging the trench. The Prophet then said, "O Allah! The real goodness is the goodness of the Here after, so please forgive the Ansar and the Muhajirin." They replied, "We are those who have given the Pledge of allegiance to Muhammad for to observe Jihad as long as we remain alive."