Hadithcore
Mishkat al-Masabih, 1207

Masruq said he asked ‘A’isha what action was most pleasing to God’s Messenger and she replied that it was what one keeps on doing. He asked at what time he got up at night and she said it was at cockcrow. (Bukhari and Muslim.)

عَنْ مَسْرُوقٍ قَالَ: سَأَلْتُ عَائِشَةَ: أَيُّ الْعَمَلِ كَانَ أَحَبَّ إِلَى رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ؟ قَالَتْ: الدَّائِمُ قُلْتُ: فَأَيُّ حِينَ كَانَ يَقُومُ مِنَ اللَّيْلِ؟ قَالَتْ: كَانَ يَقُومُ إِذا سمع الصَّارِخ

References1 variant
In-Book Reference
Book 4, Hadith 623