Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) said: I had seized a man in the mosque and made him sit, when the Messenger of Allah (peace and blessings be upon him) came. He prayed, then did the task he had come for. I was still holding on to him. Seeing this, he said: "O Ubayy! Are you still holding on to him? Whoever demands repayment of a debt from his brother, let him demand it with 'afaf (decency), wafin aw ghayra wafin (whether he receives it in full or not in full)." When I heard this, I let him go, came to him (peace and blessings be upon him) and asked: O Prophet of Allah (peace and blessings be upon him)! A little while ago you said that one should demand a debt with 'afaf, and wafin aw ghayra wafin? He (peace and blessings be upon him) said: "Yes." I said: O Prophet of Allah (peace and blessings be upon him)! What is 'afaf? He (peace and blessings be upon him) said: "It means that he does not abuse him, nor treat him harshly, nor use obscene language, nor harm him." I said: What does wafin aw ghayra wafin mean? "That he takes his right in full or leaves part of it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب التفليس / 11288