On the authority of Abu Hurayrah (may Allah be pleased with him), who said that the Messenger of Allah (PBUH) said:

If Allah has loved a servant [of His] He calls Gabriel (on whom be peace) and says: I love So-and-so, therefore love him. He (the Prophet pbuh) said: So Gabriel loves him. Then he (Gabriel) calls out in heaven, saying: Allah loves So-and-so, therefore love him. And the inhabitants of heaven love him. He (the Prophet pbuh) said: Then acceptance is established for him on earth. And if Allah has abhorred a servant [of His], He calls Gabriel and says: I abhor So-and-so, therefore abhor him. So Gabriel abhors him. Then Gabriel calls out to the inhabitants of heaven: Allah abhors So-and-so, therefore abhor him. He (the Prophet pbuh) said: So they abhor him, and abhorrence is established for him on earth.

It was related by Muslim (also by al-Bukhari, Malik, and at-Tirmidhi).