Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates that the Prophet (peace and blessings be upon him) said: "Something given as a gift (for temporary use) is to be returned, and people must abide by their (mutually agreed) conditions as long as they conform to what is right."
Al-Bazzar recorded it; its chain contains Muhammad bin Abd al-Rahman al-Baylamani, and he is extremely da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب البيوع / 6392