Musannaf Ibn Abi Shayba 13:2837

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Sufyan narrated to us, from Al-Qa’qa’ ibn Yazid, from Ibrahim, who said: If the collateral is more than what it was pledged for and it perishes, it is gone with what is in it. And if it is less, the pledger returns the surplus.