The Prophet ﷺ told us of a story where a worshipper said to a sinner to stop sinning, so the sinner told the worshipper to leave him alone.
The worshiper said: By Allah, Allah will not forgive you or admit you into Paradise! Later their souls were taken and they met in the presence of the Lord of the worlds. Allah said to the worshiper: Did you have knowledge of Me or power over what is in My hand? Allah said to the sinner: Enter Paradise by My mercy. And Allah said to the worshiper: Take him to the Hellfire.
One word ruined the entire Akhira (afterlife) of the worshipper.
