Abu Hurairah (May Allah be pleased with him) reported: The Prophet (PBUH) said, "When Allah loves a slave, calls out Jibril and says: `I love so-and-so; so love him. Then Jibril loves him. After that he (Jibril) announces to the inhabitants of heavens that Allah loves so-and-so; so love him; and the inhabitants of the heavens (the angels) also love him and then make people on earth love him".[Al-Bukhari and Muslim].
Another narration of Muslim is: Messenger of Allah, (PBUH) said: "When Allah loves a slave, He calls Jibril (Gabriel) and says: `I love so-and-so; so love him. And then Jibril loves him. Then he (Jibril) announces in the heavens saying: Allah loves so-and-so; so love him; then the inhabitants of the heavens (the angels) also love him; and then people on earth love him. And when Allah hates a slave, He calls Jibril and says: `I hate so-and-so, so hate him. Then Jibril also hates him. He (Jibril) then announces amongst the inhabitants of heavens: `Verily, Allah hates so-and-so, so you also hate him. Thus they also start to hate him. Then he becomes the object of hatred on the earth also".
[Al-Bukhari and Muslim].
This Hadith mentions the reward of love for the sake of Allah. A person who loves for the sake of Allah is not only loved by Allah but also by the inhabitants of the earth as well as the heavens. On the other hand, those who are hated by Allah are also hated by the inhabitants of the earth and the heavens. It must be borne in mind that they alone remain popular in this world who are righteous by nature - who strictly maintain the distinction between the lawful and the unlawful (Ma`ruf and Munkar). But those whose nature is defected by constant sins, cease to distinguish between right and wrong and lose their credibility. They generally hate the pious persons for the reason that every category of people loves and likes people of its own kind.