The Prophet ﷺ used to remember Allah at all times.
كان النبي ﷺ يذكر الله على كل أحيانه.
No references are available.
Muslim narrated it in "Menstruation" (373) via Ibn Abu Zaida, from his father, from Khalid bin Salama, from Bahi, from Urwa, from Ayesha, mentioning it. Bukhari cited it as a suspended narration in "Adhan" from Ayesha, using the definitive form of attribution.