وَقَالَ صلى الله عليه وسلم: ((أَقْرَبُ مَا يَكُونُ الرَّبُّ مِنَ الْعَبْدِ فِي جَوْفِ اللَّيْلِ الآخِرِ فَإِنِ اسْتَطَعْتَ أَنْ تَكُونَ مِمَّنْ يَذْكُرُ اللَّهَ فِي تِلْكَ السَّاعَةِ فَكُنْ)).
(He said: ‘The nearest the Lord comes to His servant is in the middle of the night, so if you are able to be of those who remember Allah at that time, then be so.)
At-Tirmidhi, An-Nasa'i 1/279 and Al-Hakim. See also Al-Albani, Sahih At-Tirmidhi 3/183, and Jdmi'ul-'Usool with Al-Arna'ut's checking 4/144.