Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrated the hadith of the Prophet's (peace and blessings be upon him) Hajj sermon during the days of Tashriq, that he (peace and blessings be upon him) said: "O people, whoever has something (in trust) with him, let him return it to the one whose trust it is. O people, nothing of his brother's wealth is lawful for anyone except what he gives willingly."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الغصب / 11526