It is narrated from Sayyiduna Salman al-Farisi (may Allah be pleased with him) in a marfu' report (attributed to the Prophet) that Allah, the Mighty and Majestic, says: "When My servant draws near to Me by a hand-span, I draw near to him by a forearm's length; when he draws near to Me by a forearm's length, I draw near to him by an arm-span; and when he comes to Me walking, I come to him running."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6116