Musnad Ahmad 30:304

Abu Mu'awiyah and Ibn Numayr said: We were told by Al-A'mash, from Abu Salih, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Allah, the Almighty and Majestic, says: 'I am with My servant when he remembers Me. If he remembers Me in himself, I remember him in Myself. If he remembers Me in a gathering, I remember him in a gathering better than them. If he draws near to Me by a span, I draw near to him by a cubit. If he draws near to Me by a cubit, I draw near to him by an arm's span. If he comes to Me walking, I come to him rushing.'" Ibn Numayr said in his narration: "I am as My servant thinks of Me, and I am with him when he remembers Me."