From Sahih Bukhari (Hadith 4293):
Narrated 'Aishah (ra):The Prophet (ﷺ) used to say in his bowings and prostrations, "Subhanaka Allahumma Rabbanã wa bihamdika, Allãhumma ighfirli" (Glorified be You, O Allah, our Lord! All the praises are for You. O Allah, forgive me)
Reference: Bukhari 4293