Amr bin Abasa reported,
I asked, "Messenger of Allah, is there any hour closer to Allah than another? Is there any hour in which remembrance of Him is especially sought?"He replied, "Yes. The closest the Lord 
is to His servant is in the latter part of the night. If you can be among those who remember Allah in that hour, then do so, for prayer at that time is attended and witnessed by the angels until sunrise."
Azami 2706
Sahihعن عمرو بن عبسة يقول
قلت: يا رسول الله! هل من ساعة أقرب من الأخرى؟ أو هل من ساعة يبتغى ذكرها؟ قال: نعم، إن أقرب ما يكون الرب عز وجل من العبد جوف الليل الآخر، فإن استطعت أن تكون ممن يذكر الله عز وجل في تلك الساعة فكن، فإن الصلاة محضورة مشهودة إلى طلوع الشمس.
Nasai (572) narrated it from Amr bin Mansur, who reported from Adam bin Abu Iyas, who reported from Layth bin Saad, who reported from Muawiya bin Salih, who said, Abu Yahya Salim bin Amir, Damra bin Habib, and Abu Talha Nuaym bin Ziyad reported to me, saying, We heard Abu Umama Bahili say, I heard Amr bin Abasa, and he mentioned it.Tirmidhi (3579) narrated it through Muawiya bin Salih with the same chain in abridged form, and said, "Hasan sahih gharib from this angle." I say, it is as he said, for it is sahih. Ibn Khuzayma also graded it sahih, reporting it through this route in his Sahih (1147).Abu Dawud (1277), and Bayhaqi (2/455) from him, narrated it through another route from Abu Umama, from Amr bin Abasa, and in it, "Which part of the night is most heard?" He said, "The last part of the middle of the night, so pray as much as you wish, for prayer at that time is witnessed and recorded." This isnad is sahih. Abu Umama is Sudayy bin Ajlan Bahili, a well-known companion.