Volume 3, Book 43, Number 629:
Narrated Abu Huraira (radiallaahu `anhu):
Allah’s Apostle (sallallaahu `alayhi wasallam) said, “Whoever has oppressed another person concerning his reputation or anything else, he should beg him to forgive him before the Day of Resurrection when there will be no money (to compensate for wrong deeds), but if he has good deeds, those good deeds will be taken from him according to his oppression which he has done, and if he has no good deeds, the sins of the oppressed person will be loaded on him.”
Take action NOW! If you’ve hurt someone, talked bad about them behind their back, or wronged them in any way, say sorry now. Don’t take it lightly because you can’t afford to lose your good deeds on the Day of Judgement!
P.S. if someone apologizes to you, try forgiving them. Maybe Allah will forgive you your sins for doing so. :)