Reference: Sharhus-Sunnah lil-Barbahaaree
mentions:
Do not bear witness for any of the people of Islaam (i.e. that he is a person of Paradise or of the Fire) due to a good or bad deed, since you do not know what his final action before his death will be.
You hope for Allaah’s Mercy for him and you fear for him because of his sins.
You do not know what has been destined for him at the time of his death as regards repentance and what Allaah has destined for that time if he dies upon Islaam.
You hope for Allaah’s Mercy for him and you fear for him because of his sins.
