صحيح البخاري
From Sahih Bukhari (Hadith 7505):
Narrated Abu Huraira:Allah's Messenger (ﷺ) said, "Allah said, 'I am to my slave as he thinks of Me, (i.e. I am able to do for him what he thinks I can do for him). (See Hadith No)
Reference: Bukhari 7505