On the authority of Abu Hurayrah (may Allah be pleased with him), who said that the Messenger of Allah (ﷺ) said:
Our Lord (glorified and exalted be He) descends each night to the earth's sky when there remains the final third of the night, and He says: Who is saying a prayer to Me that I may answer it? Who is asking something of Me that I may give it him? Who is asking forgiveness of Me that I may forgive him? It was related by al-Bukhari (also by Muslim, Malik, at-Tirmidhi and Abu Dawud). In a version by Muslim the Hadith ends with the words: And thus He continues till [the light of] dawn shines.
عَنْ أَبي هُرَيْرَةَ رَضِيَ اللهُ عَنْهُ أَنَّ رَسُولَ اللهِ صَلَّى الله عَلَيْهِ وَ سَلَّمَ قَالَ

يَتنزَّلُ رَبُّنَا ، تَبَارَكَ وَتَعَالَى ، كُلَّ لَيْلَةٍ إلي سَمَاءِ الدُّنْيا ، حينَ يَبْقَى ثُلُثُ اللَّيْلِ الاخِرُ ، فَيَقُولُ مَنْ يَدْعُوني فأَسْتَجِيبَ لَه ؟ مَنْ يَسْأَلُني فَأُعْطِيَهُ ؟ مَنْ يَسْتَغْفِرُني فَأَغْفِرَلَهُ ؟

رواه البخاري (وكذلك مسلم ومالك والترمذي و أبو داود)
وفي رواية لمسلم زيادة:
فَلا يَزالُ كذَلِك حَتَى يُضِيءَ الفَجْرُ
Arabic/English book reference : Hadith 35