On the authority of Abū Hurayrah (may Allah be pleased with him), who said that the Prophet (may the blessings and peace of Allah be upon him) said: Allah the Almighty says:
I am as My servant thinks I am. I am with him when he makes mention of Me. If he makes mention of Me to himself, I make mention of him to Myself; and if he makes mention of Me in an assembly, I make mention of him in an assembly better than it. And if he draws near to Me a hand’s span, I draw near to him an arm’s length; and if he draws near to Me an arm’s length, I draw near to him a fathom’s length. And if he comes to Me walking, I go to him at speed.
Related by al-Bukhārī (also by Muslim, at-Tirmidhī and Ibn Mājah).