Tafsir of At-Tawbah 9:56

"And they swear by Allah that they are indeed among you," meaning in religion. The intended meaning is that they swear they are believers like you.

"But they are not among you," in that regard, due to the disbelief of their hearts.

"But they are a people who are afraid," meaning they fear you will do to them what you do to the polytheists, so they manifest Islam out of dissimulation (taqiyya) and reinforce it with false oaths.

The root of faraq (fear) is the agitation of the soul due to the anticipation of harm. It has been said: it is the departure from a state of security to a state of fear.