Sahih Muslim 25b

Muhammad ibn Hatim ibn Maymun narrated to us; Yahya ibn Sa'id narrated to us; Yazid ibn Kaysan narrated to us, from Abu Hazim al-Ashja'i, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings be upon him) said to his uncle, ‘Say, “There is no deity except Allah,” and I will bear witness for you by it on the Day of Resurrection.’ He said, ‘Were it not that Quraysh would reproach me, saying, “Only the fear of death made him do it,” I would surely gladden your eyes with it.’ Then Allah revealed: ‘Indeed, you do not guide whom you love, but Allah guides whom He wills.’