Musnad Ahmad 30:1074

And the Messenger of Allah, may Allah bless him and grant him peace, said: "Indeed, Allah, the Mighty and Majestic, said: 'If My servant approaches Me by a span, I approach him by a cubit. And if he approaches Me by a cubit, I approach him by an arm's span. And if he approaches Me by an arm's span, I come to him—I arrive to him—more quickly.'"