Some Muslims like to claim they know who is going to heaven or hell, claiming ALL the disbeliever are going to hell or ALL the Muslims are going to heaven.
Similarly minded Christians claim everyone who doesn’t accept Christ (in the way they do) are going to hell, while they claim Jesus, on whom be peace, promised their devoted followers tickets to heaven.
This is what Allah ﷻ says in the Quran, “… you all will return to me, and I will judge between you in matters about which you disagree.” (3:55 – Kaskas)
In other words, regardless of anyone’s claims, the matter remains with God, it is God who decides who is going to heaven or hell. This isn’t something for anyone else to make grand claims or false promises about.
God sent us advice through his messengers. These words were recorded in holy books, on how to avoid hell and return to Paradise. But ultimately the keys to Paradise are, and have always been, in God’s hands, not those of any firebrand preachers!