Musnad Ahmad 1002:1

'Arim narrated to us, Mu'tamir ibn Sulayman narrated to us, from his father, al-Sumayt narrated to us, from Abu al-Siwar, Abu al-Siwar narrated to him, from his maternal uncle, who said: I saw the Messenger of Allah (peace and blessings of Allah be upon him) and people were following him, so I followed him along with them. He said: The people suddenly rushed toward me. He said: And the people remained, and the Messenger of Allah (peace and blessings of Allah be upon him) came upon me and struck me a blow, either with a palm branch, a rod, a siwak, or something that was with him. He said: By Allah, it did not hurt me. He said: I spent the night. He said: Or I said: The Messenger of Allah (peace and blessings of Allah be upon him) did not strike me except for something Allah knew in me. He said: My soul told me to come to the Messenger of Allah (peace and blessings of Allah be upon him) when I reached the morning. He said: Then Gabriel (peace be upon him) descended upon the Prophet (peace and blessings of Allah be upon him) and said: "You are a shepherd, so do not break the horns of your flock." He said: When we prayed the morning prayer, or he said: When we reached the morning, the Messenger of Allah (peace and blessings of Allah be upon him) said: "O Allah, indeed people follow me, and it does not please me that they follow me. O Allah, whoever I have struck or cursed, then make it for him an expiation and a reward," or he said: "Forgiveness and mercy," or as he said.