From Sahih Muslim (Hadith 6549):
Abu Huraira reported Allah's Apostle (ﷺ) as saying:A person visited his brother in another town and Allah deputed an Angel to wait for him on his way and when he came to him he said: Where do you intend to go? He said: I intend to go to my brother in this town. He said: Have you done any favour to him (the repayment of which you intend to get)? He said: No, excepting this that I love Mm for the sake of Allah, the Exalted and Glorious. Thereupon he said: I am a meesenger to you from, Allah: (to inform you) that Allah loves you as you love him (for His sake)
Reference: Muslim 6549