Musnad Ahmad 31:807

'Ali ibn 'Asim narrated to us, Sulayman al-Naji informed us, Abu al-Mutawakkil al-Naji informed us, from Abu Sa'id al-Khudri, who said: The Messenger of Allah (peace and blessings of Allah be upon him) prayed Dhuhr with his companions. He said: Then a man from his companions entered, and the Prophet (peace and blessings of Allah be upon him) said to him: "What detained you, O so-and-so, from the prayer?" He said: So he mentioned something he used as an excuse. He said: Then he stood to pray. The Messenger of Allah (peace and blessings of Allah be upon him) said: "Is there no man who will give charity to this one and pray with him?" He said: So a man from the people stood up and prayed with him.