Abu Hurairah (May Allah be pleased with him) said

The Messenger of Allah (ﷺ) said, "The gates of Jannah are opened on Mondays and Thursdays, and then every slave (of Allah) is granted forgiveness if he does not associate anything with Allah in worship. But the person in whose heart there is rancour against his (Muslim) brother, they will not be pardoned and with regard to them it will be said twice: 'Hold both of them until they are reconciled with each other."'

[Muslim].