Sahih Bukhari Volume 9, Book 93, Hadith Number 628.

Narrated By Abu Huraira : Perhaps the Prophet mentioned the following (as Allah’s Saying): “If My slave comes nearer to Me for a span, I go nearer to him for a cubit; and if he comes nearer to Me for a cubit; I go nearer to him for the span of outstretched arms. (See Hadith No. 502)