Abu Dharr used to narrate that the Messenger of Allah ﷺ said, "The roof of my house was opened while I was in Makkah. Jibreel descended and split open my chest, then washed it with Zamzam water. He then brought a golden basin filled with wisdom and faith, poured its contents into my chest, and closed it up."
كان أبو ذر يحدث أن رسول الله ﷺ قال: فرج عن سقف بيتي، وأنا بمكة. فنزل جبريل ففرج صدري، ثم غسله بماء زمزم، ثم جاء بطست من ذهب ممتلئ حكمة وإيمانا، فأفرغه في صدري، ثم أطبقه.
Bukhari narrated it in the Book of Prayer (349), and Muslim in the Book of Faith (163), both from the hadith of Yunus, from Ibn Shihab, from Anas bin Malik, who said, then he related it at length within the story of the Isra and Miraj.As for what is narrated about the splitting of his ﷺ chest a third time, when he was ten years old, it is daif. Abdullah bin Imam Ahmad related it (21261) at length from Ubayy bin Kaab, that Abu Hurairah was bold enough to ask the Messenger of Allah ﷺ about things no one else would ask him about. He said, "O Messenger of Allah, what is the first sign of prophethood you witnessed?" The Messenger of Allah ﷺ sat up straight and said,"You have really asked something, Abu Hurairah! I was in a desert, a boy of ten years and some months, when suddenly there was speech above my head, and there was a man saying to another man, 'Is this him?' He said, 'Yes.' Then they came to me with faces the like of which I had never seen on any creature, and scents I had never smelled from any creature, and garments I had never seen on anyone. The two of them came toward me walking, until each of them took hold of my upper arm, and I did not feel any touch from their grip. Then one of them said to his companion, 'Lay him down.' So they laid me down gently, without roughness or force. Then one of them said to his companion, 'Split open his chest.' So one of them bent down to my chest and split it open, as I saw it, without blood and without pain. He said to him, 'Take out the rancor and envy.' So he took out something like a clot, then he cast it aside and threw it away. He said to him, 'Put in compassion and mercy.' And there it was, resembling what had been taken out, but looking like silver. Then he shook the big toe of my right foot and said, 'Go forth and be safe.' So I returned with it, going about with tenderness for the young and mercy for the old."Abdullah bin Imam Ahmad narrated it this way from Muhammad bin Abdul-Rahim Abu Yahya Bazzar, who said, Yunus bin Muhammad told us, Muaz bin Muhammad bin Muaz bin Muhammad bin Ubayy bin Kaab told us, my father Muhammad bin Muaz told me, from Muaz, from Muhammad, from Ubayy bin Kaab, and he related it.Ibn Hibban recorded it in his Sahih (7155), and Hakim (3/510), both from the hadith of Muaz bin Muhammad with his chain of transmission, limiting it to the account of Abu Hurairah's boldness in asking.It contains a chain of unknown narrators, as Ali bin Madini said in Ilal, in the Musnad of Ubayy, regarding the hadith of the first sign of prophethood the Prophet ﷺ witnessed, "It was narrated by Muaz bin Muhammad bin Muaz bin Muhammad bin Ubayy, from his father, from his grandfather. It is a Madinan hadith, and its chain is entirely unknown, and we do not know Muhammad, nor his father, nor his grandfather." Ibn Hajar mentioned this in Tahdhib, in the biography of Muaz bin Muhammad bin Muaz. This also shows a lack of precision in the names, which he likewise pointed out in Tahdhib.On this topic it has also been narrated from Utba bin Abd, Shaddad bin Aws, Halimah Sadiyya, and others, but none of it is sahih except what I have mentioned.