Musnad Abu Ya'la al-Mawsili 116:56

Ahmad narrated to us, Abu Dawud narrated to us, Shu'bah informed us, from Qatadah, who heard Anas, from the Prophet (may Allah bless him and grant him peace): "Indeed, Allah says: 'If My servant 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. And if he comes to Me walking, I come to him rushing.'"