The Prophet ﷺ said, "On the Day of Resurrection, some Muslims will come bearing sins as great as mountains, and Allah will forgive them and place those sins upon the Jews and Christians."
ى، عن النبي ﷺ قال: يجيء يوم القيامة ناس من المسلمين بذنوب أمثال الجبال، فيغفرها الله لهم ويضعها على اليهود والنصارى.
Muslim narrated it in the Book of Repentance (2767:51) from Muhammad bin Amr bin Abbad bin Jabala bin Abu Rawwad, who said, Harmi bin Umara narrated to us, who said, Shaddad Abu Talha Rasibi narrated to us, from Ghaylan bin Jareer, from Abu Burda, from his father, and he related it.The meaning of the hadith about deliverance from the Fire has posed a difficulty for many people, because it seems to contradict the statement of Allah Most High, "No bearer of burdens will bear the burden of another" [Isra 17:15], and His statement, "And that man will have nothing except what he strives for" [Najm 53:39].What appears to me is that the conduct of the People of the Book, the Jews and Christians, was a cause for many people not entering Islam, because they knew the Prophet ﷺ and what he brought better than others did, since mention of him ﷺ was found in their books. Allah Most High says, "Those who follow the Messenger, the unlettered prophet, whom they find written in the Torah and the Injil, who enjoins upon them what is right and forbids them what is wrong, and makes lawful for them the good things and prohibits for them the evil, and relieves them of their burden and the shackles that were upon them. So those who have believed in him, honored him, supported him, and followed the light that was sent down with him, those are the successful ones" [Araf 7:157].So the fate of these people became like the fate of the disbelievers, "And those who disbelieve say to those who believe, 'Follow our way, and we will carry your sins.' But they will not carry anything of their sins. Indeed, they are liars" [Ankabut 29:12].Except for whoever Allah Most High has guided by His mercy. So this guided man comes on the Day of Resurrection with sins upon him that may be like mountains. Allah Most High then multiplies the punishment of the Jews and Christians whose conduct was in particular a cause for many people not entering Islam, and this guided man had very nearly been one of them, except that Allah's mercy reached him, so he entered Islam. These Jews and Christians then bear his sins, and thus his deliverance from the Fire is called "fakak," just as freeing a man from the hand of the pledgeholder is called "fakak."