It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said in the sermon of the Farewell Hajj: "Nothing of his brother's wealth is lawful for any person except what he gives willingly; and do not wrong (one another), and do not turn back after me into disbelief, killing one another."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الغصب / 11524