Sahih Bukhari Volume 008, Book 073, Hadith Number 066.

Narated By Abu Huraira : The Prophet said, "If Allah loves a person, He calls Gabriel saying: 'Allah loves so and so; O Gabriel, love him.' Gabriel would love him, and then Gabriel would make an announcement among the residents of the Heaven, 'Allah loves so-and-so, therefore, you should love him also.' So, all the residents of the Heavens would love him and then he is granted the pleasure of the people of the earth."