Language:
كتاب مواقيت الصلاة
9
Times of the Prayers
(16)
Chapter: Superiority of the 'Asr prayer
(16)
باب فَضْلِ صَلاَةِ الْعَصْرِ
Sahih al-Bukhari 555

Narrated Abu Huraira:

Allah's Messenger (ﷺ) said, "Angels come to you in succession by night and day and all of them get together at the time of the Fajr and `Asr prayers. Those who have passed the night with you (or stayed with you) ascend (to the Heaven) and Allah asks them, though He knows everything about you, well, "In what state did you leave my slaves?" The angels reply: "When we left them they were praying and when we reached them, they were praying."

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، قَالَ حَدَّثَنَا مَالِكٌ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ يَتَعَاقَبُونَ فِيكُمْ مَلاَئِكَةٌ بِاللَّيْلِ وَمَلاَئِكَةٌ بِالنَّهَارِ، وَيَجْتَمِعُونَ فِي صَلاَةِ الْفَجْرِ وَصَلاَةِ الْعَصْرِ، ثُمَّ يَعْرُجُ الَّذِينَ بَاتُوا فِيكُمْ، فَيَسْأَلُهُمْ وَهْوَ أَعْلَمُ بِهِمْ كَيْفَ تَرَكْتُمْ عِبَادِي فَيَقُولُونَ تَرَكْنَاهُمْ وَهُمْ يُصَلُّونَ، وَأَتَيْنَاهُمْ وَهُمْ يُصَلُّونَ ‏"‏‏.‏
Reference : Sahih al-Bukhari 555
In-book reference : Book 9, Hadith 32
USC-MSA web (English) reference : Vol. 1, Book 10, Hadith 530
  (deprecated numbering scheme)