Musnad Ahmad 30:781

Yazid narrated to us, Ibn Abi Dhi'b informed us, from al-Zuhri, from Abu Salamah, from Abu Hurairah, who said: When the Messenger of Allah (peace and blessings of Allah be upon him) would attend a funeral, he would ask: "Does your companion have any debt?" If they said: "Yes," he would ask: "Does he have the means to repay it?" If they said: "Yes," he would pray over him. If they said: "No," he would say: "Pray over your companion." But when Allah (the Almighty and Majestic) granted him the conquests, he said: "I am closer to the believers than their own selves. So whoever leaves behind a debt, it is upon me [to pay it], and whoever leaves behind wealth, it is for his heirs."