Musnad Ahmad 30:2720

Hajjaj narrated to us, he said: Layth narrated to us, he said: ‘Uqayl narrated to us, from Ibn Shihab, from Abu Salamah ibn ‘Abd al-Rahman, from Abu Hurayrah, that the Messenger of Allah (ﷺ) would have the deceased man upon whom there was debt brought to him. He would ask: "Has he left anything for the repayment of his debt?" If he was told that he had left enough for repayment, he would pray over him. Otherwise, he would say to the Muslims: "Pray over your companion." When Allah granted him the conquests, he stood and said: "I am closer to the believers than their own selves. So whoever among the believers dies and leaves behind a debt, then its repayment is upon me, and whoever leaves behind wealth, it is for his heirs."