If a man were killed in the path of Allah, then brought back to life while in debt, he would not enter Paradise until his debt was paid

It is narrated from Sayyiduna Muhammad bin Jahsh (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) was sitting at the place where the funeral biers are placed. He (peace and blessings be upon him) raised his head towards the sky, then lowered his gaze, placed his hand on his forehead and said: "Subhan Allah! Subhan Allah! What severity Allah has sent down!" Seeing this, we became frightened and remained silent. When the next day came, I asked the Messenger of Allah (peace and blessings be upon him): "O Messenger of Allah, what was the severity that was sent down?" He (peace and blessings be upon him) said: "Concerning debt. By the One in whose hand is the soul of Muhammad (peace and blessings be upon him)! If a man were martyred in the path of Allah, then brought back to life, then martyred, then brought back to life, while he owed a debt, he would not enter Paradise until his debt was paid off."
This hadith has a sahih (authentic) chain, but the two Shaykhs did not record it.

It is narrated from Sayyiduna Samurah bin Jundub (may Allah be pleased with him) that one day the Messenger of Allah (peace and blessings be upon him) led the prayer. When he finished, he asked: "Is there anyone here from Banu so-and-so?" The people remained silent (and whenever he (peace and blessings be upon him) asked them about something, they would fall silent out of respect). He (peace and blessings be upon him) asked again: "Is there anyone here from Banu so-and-so?" A man said: "Yes, this is so-and-so." He (peace and blessings be upon him) said: "Your companion has been held back at the gate of Paradise because of a debt he owed." Upon this, a man said: "His debt is my responsibility," and he paid it off.

It is narrated from Sayyiduna Samurah bin Jundub (may Allah be pleased with him) that one day the Messenger of Allah (peace and blessings be upon him) led the prayer and asked three times: "Is there anyone here from Banu so-and-so?" When no one answered, he (peace and blessings be upon him) said: "The man among you who has died has been held back from Paradise because of the debt he owed. Now, if you wish, ransom him (by paying it), and if you wish, hand him over to the punishment of Allah."
This hadith is sahih (authentic) on the condition of the two Shaykhs, but they did not record it because of a difference over it in the narration of Sa'id bin Masruq al-Thawri.

It is narrated from Sayyiduna Samurah bin Jundub (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said something similar.
(Imam al-Hakim says that it is not possible to declare the narrations of such reliable Imams as Isma'il bin Abi Khalid and Firas bin Yahya in the chain of this hadith defective on the basis of narrations like that of Sa'id bin Masruq.)

It is narrated from Sayyiduna Uqbah bin Amir al-Juhani (may Allah be pleased with him) that he said: I heard the Messenger of Allah (peace and blessings be upon him) say to his Companions: "Do not make your souls fearful." It was said: "O Messenger of Allah, how do we make our souls fearful?" He (peace and blessings be upon him) said: "Through debt."
This hadith has a sahih (authentic) chain, but the two Shaykhs did not record it.