Musnad Ahmad 175:3

Waki’ narrated to us, Zam’ah narrated to us, from al-Zuhri, from Ibn Ka’b ibn Malik, from his father, that the Prophet, peace and blessings of Allah be upon him, passed by him while he was holding a man to [repay] two uqiyahs. The Prophet, peace and blessings of Allah be upon him, said to the man: "Like this," meaning: "Relieve him of half of it." The man said: "Yes, O Messenger of Allah." Then the Prophet, peace and blessings of Allah be upon him, said to the man: "Pay him the remainder of his right."