Majma al-Zawaid — Hadith 13843

Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) narrates: Sayyiduna Abu Hurayrah (may Allah be pleased with him) had the boldness to ask the Prophet (peace and blessings be upon him) about things that no one else would ask him about. He said: "O Messenger of Allah, what was the first thing you saw concerning the matter of prophethood?" The Prophet (peace and blessings be upon him) sat up straight and said: "O Abu Hurayrah, you have asked an important question. Once I was in the desert, when I was ten years and some months old. Meanwhile I heard the sound of talking above me, and one person was saying to another: 'Is this he?' The other replied: 'Yes.' Then the two of them came towards me from the front, with faces such as I had never seen on any creature, and a fragrance such as I had never found from any creature, and their clothes were such that I had never seen such clothing on anyone's body. The two of them came walking to me until each of them took hold of my upper arm, but I did not feel the touch of either of them. One of them said to the other: 'Lay him down.' The two of them laid me down without any constriction and without breaking any limb. One of them said to the other: 'Split open his chest.' Then one of them bent over my chest and split it open, yet no blood came out and no pain was felt. He said to the other: 'Remove rancour and envy.' So he took out something like a clot of blood and then threw it aside. He said to the other: 'Put mercy and compassion into it.' Then something like silver was brought, similar to what had been taken out. Then he shook the big toe of my right foot and said: 'Get up and be safe.' When I came back from there, my state was that I was gentle towards the young and merciful towards the old."
Abdullah (bin Ahmad) recorded it, and its narrators are thiqat (trustworthy); Ibn Hibban declared them trustworthy.