Sahih al-Bukhari 1132

حَدَّثَنَا مُحَمَّدُ بْنُ سَلاَمٍ قَالَ أَخْبَرَنَا أَبُو الأَحْوَصِ عَنِ الأَشْعَثِ قَالَ إِذَا سَمِعَ الصَّارِخَ قَامَ فَصَلَّى‏

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