Sahih Bukhari | Volume 5 | Hadith Number 140

Narrated by Anas bin Malik
On the day of the battle of the Trench (i.e. Ghazwat-ul-Khandaq) the Ansar used to say, "We are those who have given the pledge of allegiance to Muhammad for Jihad (i.e. holy fighting) as long as we live." The Prophet , replied to them, "O Allah! There is no life except the life of the Hereafter; so please honour the Ansar and the Emigrants."