Musnad Ahmad 175:28

Hassan narrated to us, he said: Ibn Lahi'ah narrated to us, he said: Abd al-Rahman al-A'raj narrated to us, from Abdullah ibn Ka'b, from Ka'b ibn Malik, that he had a debt owed to him by Abdullah Abu Hadrad al-Aslami. He met him and held onto him until their voices rose. The Messenger of Allah, peace and blessings of Allah be upon him, passed by them and said: "O Ka'b." He gestured with his hand as if he were saying: "Half." So he took half of what was owed to him and left the other half.