Zadhan says: I was sitting with Abdullah bin Umar (may Allah be pleased with them) when he called one of his slaves and set him free. Then he said: I did not even get as much reward for freeing him as this, and he picked up something from the ground with his hand. I heard the Messenger of Allah (peace and blessings be upon him) say: Whoever imposes a punishment on his slave for something he did not commit, or slaps him, then its expiation is that he should set him free.