Riyad as-Salihin

'Aishah (May Allah be pleased with her) reported: Prior to his demise, the Messenger of Allah (ﷺ) used to supplicate frequently: Subhan Allahi wa bihamdihi; Astaghfirullaha wa atubu ilaihi (Allah is free from imperfection, and I begin with praising Him. I beg forgiveness from Allah and I turn to Him in repentance."

[Al-Bukhari and Muslim].