Anas ibn Malik reported: The Messenger of Allah, peace and blessings be upon him, said to me:

يَا بُنَيَّ إِنْ قَدَرْتَ أَنْ تُصْبِحَ وَتُمْسِيَ لَيْسَ فِي قَلْبِكَ غِشٌّ لِأَحَدٍ فَافْعَلْ

Young man, if you are able every morning and evening to remove any rancor from your heart towards anyone, do so.

Then, the Prophet said to me:

يَا بُنَيَّ وَذَلِكَ مِنْ سُنَّتِي وَمَنْ أَحْيَا سُنَّتِي فَقَدْ أَحَبَّنِي وَمَنْ أَحَبَّنِي كَانَ مَعِي فِي الْجَنَّة

 

Young man, that is my Sunnah. Whoever revives my Sunnah has loved me, and whoever loves me will be with me in Paradise.

Source: Sunan al-Tirmidhī 2678, Grade: Hasan