Abu Huraira reported: The Messenger of Allah, peace be and blessings on him, said, “Allah the Exalted says: I am as my servant expects me and I am with him as he remembers me. If he remembers me in himself, then I will remember him in myself. If he mentions me in a gathering, then I will mention him in a greater gathering. When he draws near to me by the span of his hand, I draw near him by the length of a cubit. When he draws near me by the length of a cubit, I draw near him by the length of a fathom. When he comes to me walking, I will come to him running.”

Source: Sahih Bukhari 6970, Sahih Muslim 2675

Grade: Muttafaqun Alayhi (authenticity agreed upon) according to Al-Bukhari and Muslim

عَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ قَالَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ اللَّهُ تَعَالَى أَنَا عِنْدَ ظَنِّ عَبْدِي بِي وَأَنَا مَعَهُ إِذَا ذَكَرَنِي فَإِنْ ذَكَرَنِي فِي نَفْسِهِ ذَكَرْتُهُ فِي نَفْسِي وَإِنْ ذَكَرَنِي فِي مَلَإٍ ذَكَرْتُهُ فِي مَلَإٍ خَيْرٍ مِنْهُمْ وَإِنْ تَقَرَّبَ إِلَيَّ بِشِبْرٍ تَقَرَّبْتُ إِلَيْهِ ذِرَاعًا وَإِنْ تَقَرَّبَ إِلَيَّ ذِرَاعًا تَقَرَّبْتُ إِلَيْهِ بَاعًا وَإِنْ أَتَانِي يَمْشِي أَتَيْتُهُ هَرْوَلَةً

6970 صحيح البخاري كِتَاب التَّوْحِيدِ إن رحمتي تغلب غضبي

2675 صحيح مسلم كِتَاب التَّوْبَةِ بَاب فِي الْحَضِّ عَلَى التَّوْبَةِ وَالْفَرَحِ بِهَا

http://dailyhadith.abuaminaelias.com/2011/01/07/the-virtue-of-repentance/