Narrated 'Uqbah bin 'Amir:
"The Messenger of Allah (ﷺ) ordered me to recite Al-Mu'awwidhatain at the end of every Salat." (RU)
English reference (RU): Vol. 5, Book 42, Hadith 2903 (RU)
Arabic reference (RU): Book 45, Hadith 3150 (RU)