John Gill Commentary Acts 22:17

"And it came to pass, that, when I had returned to Jerusalem, and while I prayed in the temple, I fell into a trance," — Acts 22:17 (ASV)

And it came to pass, that when I had come again to
Jerusalem
Which was three years after his conversion; for he did not immediately return to Jerusalem, but went into Arabia; and when he returned to Damascus, which was three years after he came to Jerusalem; see (Galatians 1:17Galatians 1:18)

even while I prayed in the temple ;
the temple was a house of prayer; people resorted here for that purpose; and as the apostle had been used to it, he continued this custom, and during the time of prayer he fell into an ecstasy:

I was in a trance :
and knew not whether he was in the body, or out of the body: whether this was the time he refers to in (2 Corinthians 12:2) is not certain, though probable.