In another report the Prophet ﷺ said, “On the Day of Resurrection some people from the Muslims will arrive bearing sins as massive as mountains, yet Allah will forgive them.” Narrated by Muslim.

His words, “He will assign to every Muslim a Jew or a Christian and say, ‘This person is your ransom from the Fire,’ ” have the same meaning as the ḥadith of Abū Hurayrah (may Allah be pleased with him): “Each person has a dwelling in Paradise and a dwelling in Hell. When the believer enters Paradise, the disbeliever takes his place in Hell, for he deserves that on account of his unbelief.”

The expression “your ransom” (fakākuka) means that you yourself were liable to enter the Fire, and this person becomes your ransom. Allah, exalted is He, has decreed for Hell a certain number that will fill it; when the disbelievers enter it because of their sins and their rejection of faith, they serve as a ransom for the Muslims. Allah knows best.

22/433 – Ibn ʿUmar (may Allah be pleased with them both) said: I heard the Messenger of Allah ﷺ say, “On the Day of Resurrection the believer will be brought near to his Lord until He places His screen over him, then He will remind him of his sins, saying, ‘Do you acknowledge such-and-such a sin? Do you acknowledge such-and-such a sin?’ He will answer, ‘My Lord, I do acknowledge them.’ He will say, ‘I concealed them for you in the worldly life, and today I forgive them for you,’ and he will be handed the record of his good deeds.” Agreed upon.

“His screen” (kanafa) means His covering and mercy.