From Sahih Bukhari (Hadith 6330):
Narrated Warrad:(the freed slave of Al-Mughira bin Shu`ba) Al-Mughira wrote to Muawiya bin Abu Sufyan that Allah's Messenger (ﷺ) used to say at the end of every prayer after the Taslim, "La ilaha illa-l-lahu wahdahu la sharika lahu; lahu-l-mulk wa lahu-l-hamd, wahuwa 'ala kulli shai'n qadir. Allahumma la mani'a Lima a taita, wa la mu'ta Lima mana'ta, wa la yanfa'u dhal-jaddu minkal-jadd
Reference: Bukhari 6330