Salih bin Abu Turaif narrates: I asked Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him): Did you hear the Prophet (peace and blessings of Allah be upon him) say anything about this verse? "Soon those who disbelieved will wish that they had been Muslims."
Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) replied: Yes, I heard the Prophet (peace and blessings of Allah be upon him) say: "Allah Almighty will take out some people from among the believers from Hell; this will happen after He has punished them." The Prophet (peace and blessings of Allah be upon him) said: When Allah has entered these people into Hell along with the polytheists, the polytheists will say: Did you not used to say in the world that you are friends? Then why are you with us in Hell? When Allah hears this, He will permit intercession, so the angels and the prophets will intercede for these people until, by Allah's command, they will come out (of Hell). When they are taken out, those people (the disbelievers) will say: Oh, would that we were like them, and intercession would be granted to us, and we too would come out of Hell. So this is the meaning of Allah's statement: "Soon those who disbelieved will wish that they had been Muslims."
The Prophet (peace and blessings of Allah be upon him) said: The name of these people in Paradise will be "Jahannami" (Hell-dwellers) because their faces will have become blackened. They will say: O our Lord, remove this name from us. The Prophet (peace and blessings of Allah be upon him) said: Then the Lord will command them to bathe in a river of Paradise, and their (blackness) will be removed.