Musannaf Ibn Abi Shayba 13:1528

Abu Bakr narrated to us, he said: Ali ibn Mushir narrated to us, from Isma'il, from Mahan, who said: Ibn Mas'ud passed by a man who was weighing a small heap [of goods] and he had made it tip the scale. He said: "Divide the tongue of the scale, and when it is balanced, then add to it from your wealth whatever you wish."