The Messenger of Allah ﷺ, during the night prayer, used to say after pronouncing "Allahu Akbar"... and then he mentioned its meaning.
حدثنا أبو كامل حدثنا خالد يعني ابن الحارث حدثنا عمران بن مسلم أن قيس بن سعد حدثه قال حدثنا طاوس
أن رسول الله ﷺ كان في التهجد يقول بعد ما يقول الله أكبر ثم ذكر معناه
No references are available.
Muslim collected it in Sahih Muslim, Prayer of the Traveler, chapter on the prayer and supplication of the Prophet ﷺ at night, hadith no. 769, from the hadith of Imran bin Muslim Qasir, through this chain.