Abu Hurairah reported,
The Messenger of Allah ﷺ said that Allah 
says, "I am with My servant whenever he remembers Me. If he remembers Me within himself, I remember him within Myself. If he remembers Me in a gathering, I remember him in a better gathering. If he draws near to Me by a hand's span, I draw near to him by a forearm's length. If he draws near to Me by a forearm's length, I draw near to him by an arm's span. And if he comes to Me walking, I come to him at a swift pace."Ibn Numayr in his version added, "I am as My servant thinks of Me, and I am with him wherever he remembers Me."
Ahmad 7422
Sahihحدثنا أبو معاوية وابن نمير قالا حدثنا شعبة عن الأعمش عن أبي صالح
عن أبي هريرة قال
قال رسول الله ﷺ يقول الله عز وجل أنا مع عبدي حين يذكرني فإن ذكرني في نفسه ذكرته في نفسي وإن ذكرني في ملإ ذكرته في ملإ هم خير منهم وإن اقترب إلي شبرا اقتربت إليه ذراعا وإن اقترب إلي ذراعا اقتربت إليه باعا فإن أتاني يمشي أتيته هرولة وقال ابن نمير في حديثه أنا عند ظن عبدي بي وأنا معه حيث يذكرني
Its isnad is sahih. Abu Muawiya Muhammad bin Khazim - with the dotted kha - the blind, his biography has already been given at 6499. We add here that Ibn Saad mentioned him in al-Tabaqat 6:273-274, and Ibn Abu Hatim in al-Jarh wal-Tadil 2/3:246-248.Ibn Numayr is Abdullah bin Numayr bin Abdullah bin Abu Hiyya al-Kharifi, whose reliability was already established at 1059. We add here that Ibn Saad gave his biography at 6:274-275, and traced his lineage further back than mentioned elsewhere. Ibn Abu Hatim also gave his biography at 2/2:186.The hadith was narrated by Tirmidhi 4:290 from Abu Kurayb, from Abu Muawiya and Ibn Numayr, with this isnad, and its beginning in his narration reads, "I am according to my servant's expectation of Me, and I am with him when he remembers Me," that is, following the wording of Ibn Numayr. He did not distinguish between his narration and that of Abu Muawiya with the detail that Imam Ahmad has clarified here. Tirmidhi said, This is a hasan sahih hadith.Bukhari narrated it at 13:325-328, from Umar bin Hafs from his father, and Muslim at 2:306-307, through the route of Jareer, both of them from Amash, with this isnad. He then narrated it, without mentioning its wording, from Abu Bakr bin Abu Shayba and Abu Kurayb, both of them from Abu Muawiya from Amash, with the same chain.Tirmidhi said, after his narration, "It is also related from Amash, in explanation of this hadith, 'Whoever draws near to Me a hand span, I draw near to him an arm's length,' meaning through forgiveness and mercy." This is how the scholars of hadith have explained it. They said, its meaning is that if the servant draws near to Me through obeying Me and through what I have commanded, My forgiveness and My mercy hasten toward him.