They were bowing in the dawn prayer.
حدثنا هناد حدثنا وكيع عن سفيان عن عبد الله بن دينار
كانوا ركوعا في صلاة الصبح
No references are available.
Graded as agreed upon [by Bukhari and Muslim]. Bukhari reported it in the Book of Prayer, chapter on what has been mentioned regarding the qibla, etc., hadith no. 403, and Muslim, hadith no. 526, from the hadith of Abdullah bin Dinar, with this chain.