Sahih al-Bukhari, Hadith 6461 ⓘ
Narrated Masruq: I asked `Aisha "What deed was the most beloved to the Prophet?" She said, "The regular constant one." I said, "At what time did he use to get up at night (for the Tahajjud night prayer)?' She said, "He used to get up on hearing (the crowing of) the cock (the last third of the night).
حَدَّثَنَا عَبْدَانُ، أَخْبَرَنَا أَبِي، عَنْ شُعْبَةَ، عَنْ أَشْعَثَ، قَالَ سَمِعْتُ أَبِي قَالَ، سَمِعْتُ مَسْرُوقًا، قَالَ سَأَلْتُ عَائِشَةَ ـ رضى الله عنها ـ أَىُّ الْعَمَلِ كَانَ أَحَبَّ إِلَى النَّبِيِّ صلى الله عليه وسلم قَالَتِ الدَّائِمُ. قَالَ قُلْتُ فَأَىَّ حِينٍ كَانَ يَقُومُ قَالَتْ كَانَ يَقُومُ إِذَا سَمِعَ الصَّارِخَ.
also referenced under: Book 81, Hadith 50 (In-Book) & Volume 8, Book 76, Hadith 468 (USC-MSA)