During the two Rak'ah of Tawaf, the Messenger of Allah recited the two Surat of Ikhlas, "Say: O you disbelievers!" and: "Say: He is Allah, (the) One."
Jami` at-Tirmidhi Book 9, Hadith 62
← Previous Hadith the Prophet said: "O Banu Abd Manaf! Do not prevent anyone from performing Tawaf around this House, and Salat, whichever hour it is of the night or day."

Jami` at-Tirmidhi Book 9, Hadith 61 Next Hadith → that he considered it recommended for the two Rak'ah of Tawaf to recite: Say: "O you disbelievers!" and: Say: "He is Allah, (the) One."

Jami` at-Tirmidhi Book 9, Hadith 63