Fiqh-us-Sunnah Volume 2, Supererogatory Prayer, Fiqh 2.005.

In the first rak’ah, after al-Fatiha, he would recite the verse: “Say: We believe in Allah, and the revelation given to us and what was revealed to Abraham, Ismail, Isaac, Jacob and the tribes, and [in what] was given to Moses and Jesus, and what was given to the Prophets, from their Lord and we do not differentiate between any of them. And we are Muslims.”