Sahih Adab al-Mufrad

Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates from the Prophet (peace and blessings of Allah be upon him) that he said: "A man set out to visit a brother of his in another town, so Allah appointed an angel to wait for him on his way. The angel asked: 'Where are you going?' He replied: 'To visit a brother of mine who lives in this town.' The angel asked: 'Has he done you any favor which you are going to repay?' He replied: 'No, I only love him for the sake of Allah.' The angel said: 'I am a messenger to you from Allah (to inform you) that Allah loves you as you love him.'"