On the authority of Abu Hurayrah (may Allah be pleased with him) who said:
The Messenger of Allah (peace and blessings of Allah be upon him) said, "Verily Allah ta'ala has said: 'Whosoever shows enmity to a wali (friend) of Mine, then I have declared war against him. And My servant does not draw near to Me with anything more loved to Me than the religious duties I have obligated upon him. And My servant continues to draw near to me with nafil (supererogatory) deeds until I Love him. When I Love him, I am his hearing with which he hears, and his sight with which he sees, and his hand with which he strikes, and his foot with which he walks. Were he to ask [something] of Me, I would surely give it to him; and were he to seek refuge with Me, I would surely grant him refuge.' "[Al-Bukhari]
Reference: 40 Hadith Nawawi 38
English translation: Hadith 38