Musnad Abu Ya'la al-Mawsili 130:26

Ja'far ibn Mihran narrated to us, 'Abd al-Warith ibn Sa'id narrated to us, 'Abd al-'Aziz ibn Suhayb narrated to us, from Anas ibn Malik, who said: The Emigrants (Muhajirun) and the Helpers (Ansar) were digging the trench around Medina, and they were carrying the dirt on their backs, saying: "We are those who pledged allegiance to Muhammad upon Islam, for as long as we remain." He said: And the Messenger of Allah, peace and blessings of Allah be upon him, was saying, responding to them: "O Allah, there is no good except the good of the Hereafter, so bless the Helpers and the Emigrants." He said: And they would be brought a handful of barley, and it would be prepared for them with rancid fat, which was repulsive in the throat and had a foul odor, and it would be placed before the people.