Musannaf Ibn Abi Shayba 13:2971

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Isra’il narrated to us, from Jabir, from ‘Ata’, Salim, and ‘Amir, they said: If the mortgagor dies and he has a debt upon him, then the mortgagee has more right to it than the [other] creditors until he is paid in full.