A Muslim does not doom another Muslim to Hell, nor dictate whether or not Allah will forgive him his sins

The Prophet Muhammad (peace be upon him) said:

“A man said, ‘By Allah, Allah will not forgive So-and-so!’

At this Allah the Almighty said, ‘Who is he who swears by Me that I will not forgive So-and-so? I have forgiven So-and-so and I have nullified your [own good] deeds!’”

(Sahih Muslim)

Allah the Most High tell us in His Book, “And let every soul look to what it has put forth for tomorrow.” A Muslim should busy himself in holding himself accountable and looking at his own sins. It is not his job or concern to do so for anyone else.

Jabir ibn Abdullah (may Allah be pleased with him) tells us a remarkable story from the Sunnah about a companion who killed himself. Despite the fact that suicide is a major sin, Allah the Merciful forgave the companion and entered him into Paradise:

Jabir reported that at-Tufayl ibn ’Amr ad-Dawsi migrated to the Prophet, peace be upon him, accompanied by another man from his tribe.

They both disliked their stay in Madinah (because they were away from their people). At-Tufayl’s friend became very sick and was so overwhelmed with pain that he used an arrow’s blade to cut his fingers at the knuckles, causing bleeding that led to his death.

At-Tufayl then saw his friend in a dream; in the dream his friend looked well but had his hands wrapped up.

He asked him, “What did your Lord do to you?”

He replied, “He forgave me because I migrated to His Prophet.”

He asked him, “But why are your hands wrapped like this?”

He replied that he was told (by Allah), “We will not repair for you what you have damaged.”

At-Tufayl related his dream to the Prophet, who said, “O Allah, forgive his hands as well!”

(Sahih Muslim)

An-Nawawi, may Allah have mercy on him, commented on this hadith saying:

“As for the rules taken from this hadith, then this hadith is proof for a great principle of Ahl As-Sunnah which is that the (Muslim) who kills himself or commits another (major) sin and dies without repenting, he is not a disbeliever and it cannot be declared that he will enter the Hellfire. Rather he is under the will (of Allah).”

(Sharh An-Nawawi ’ala Muslim)