Sahih al-Bukhari 1132

Arabic

حَدَّثَنِي عَبْدَانُ، قَالَ أَخْبَرَنِي أَبِي، عَنْ شُعْبَةَ، عَنْ أَشْعَثَ، 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.‏ قُلْتُ مَتَى كَانَ يَقُومُ قَالَتْ يَقُومُ إِذَا سَمِعَ الصَّارِخَ‏

English translation

Narrated Masruq:I asked `Aisha which deed was most loved by the Prophet. She said, "A deed done continuously." I further asked, "When did he used to get up (in the night for the prayer)." She said, "He used to get up on hearing the crowing of a cock

Reference: Sahih al-Bukhari 1132, Book of Prayer at Night (Tahajjud). English translation by Dr. Muhammad Muhsin Khan.