Bulugh al-Maram 2 The Book of Prayer كتاب الصلاة 33

وَزَادَ أَحْمَدُ فِي آخِرِهِ قِصَّةَ قَوْلِ بِلَالٍ فِي آذَانِ اَلْفَجْرِ: { اَلصَّلَاةُ خَيْرٌ مِنَ اَلنَّوْمِ } 1 . 1 – انظر ما قبله.

Ahmad added to the end of the above Hadith, the story of BIlal’s statement in the Fajr Adhan (morning prayer call): as-Salatu khairun minan-nawm – “Prayer is better than sleep”.