The Messenger of Allah ﷺ recited the two surahs of sincerity in the two rakahs of tawaf, "Say, O disbelievers" [Kafirun 109:1] and "Say, He is Allah, the One" [Ikhlas 112:1].
أخبرنا أبو مصعب المدني قراءة عن عبد العزيز بن عمران عن جعفر بن محمد عن أبيه
أن رسول الله ﷺ قرأ في ركعتي الطواف بسورتي الإخلاص قل يا أيها الكافرون وقل هو الله أحد
[Sahih] Its origin is found in Muslim, Hajj, chapter on the Hajj of the Prophet, may Allah bless him and grant him peace, no. 1218, and Nasai, 5/236, no. 2966, and others. Abdul-Aziz was corroborated by Hatim bin Ismail.