Musnad Ahmad 1301:15

Muhammad ibn Bakr narrated to us, he said: Maymun—meaning Abu Muhammad al-Mura'i al-Tamimi—narrated to us, he said: Yahya ibn Abi Kathir narrated to us, from Yusuf ibn Abdullah ibn Salam, who said: I accompanied Abu al-Darda' to learn from him. When death approached him, he said: "Inform the people of my death." So I informed the people of his death, and I came back and the house and what was around it were filled. He said: I said: "I have informed the people of your death, and the house and what is around it are filled." He said: "Take me out." So we took him out. He said: "Seat me." He said: "So we seated him." He said: "O people, I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: 'Whoever performs ablution and perfects the ablution, then prays two rak'ahs, completing them, Allah will give him what he asks for, sooner or later.'" Abu al-Darda' said: "O people, beware of turning [the head/attention], for there is no prayer for one who turns. If you are overcome in the voluntary prayer, do not be overcome in the obligatory prayer."