Musnad Ahmad 32:458

Hashim narrated to us, Sulayman narrated to us, from Thabit, from Anas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) sent Basbas as a scout to see what the caravan of Abu Sufyan had done. He came back, and there was no one in the house except me and the Messenger of Allah (peace and blessings of Allah be upon him)—he said: I do not know what he excepted of some of his wives—and he told him the news. He said: The Messenger of Allah (peace and blessings of Allah be upon him) went out and spoke, saying: "We have a pursuit, so whoever has his mount present, let him ride with us." Men began to ask his permission regarding mounts they had in the upper part of Medina. He said: "No, except for those whose mount is present." The Messenger of Allah (peace and blessings of Allah be upon him) and his companions set out until they reached Badr before the polytheists. The polytheists arrived, and the Messenger of Allah (peace and blessings of Allah be upon him) said: "Let no one among you advance toward anything until I am the one who gives the order." The polytheists drew near, and the Messenger of Allah (peace and blessings of Allah be upon him) said: "Rise to a Paradise whose width is the heavens and the earth." 'Umayr ibn al-Humam al-Ansari said: O Messenger of Allah, a Paradise whose width is the heavens and the earth? He said: "Yes." He said: "Bakh, bakh!" (an expression of amazement and joy). The Messenger of Allah (peace and blessings of Allah be upon him) said: "What compels you to say 'bakh, bakh'?" He said: No, by Allah, O Messenger of Allah, except for the hope that I might be among its people. He said: "Then you are among its people." He said: He took out some dates from his quiver and began to eat from them, then he said: If I were to live until I finish these dates of mine, it would indeed be a long life. He said: Then he threw away what he had with him of the dates, then he fought them until he was killed.