Musnad Ahmad 25:1141

Yahya ibn Adam narrated to us, Israel narrated to us, from ‘Ata’ ibn al-Sa’ib, from Sa’id ibn Jubayr, from Ibn Abbas, who said: "When [the verse] 'And do not approach the wealth of the orphan except in the way that is best' [Al-An'am: 152] was revealed, they separated the wealth of the orphans, until the food began to spoil and the meat began to rot. This was mentioned to the Prophet, peace and blessings of Allah be upon him, so [the verse] was revealed: 'And if you mix your affairs with theirs, they are your brothers. And Allah knows the corrupter from the reformer' [Al-Baqarah: 220]." He said: So they mixed their affairs with theirs.