en_tn/act/09/03.md

(After the high priest gave Saul the letters, Saul left for Damascus)

As he was traveling

Saul left Jerusalem and is now traveling to Damascus.

it happened that

This is an expression to mark a change in the story, that something different is about to happen.

there shone all around him a light out of heaven

"a light from the sky shone all around him"

he fell upon the ground

It is ambiguous between 1) "Saul threw himself to the ground" or 2) "The light caused him to fall to the ground" or 3) "Saul fell to the ground like one who fainted and fell." Saul did not fall accidentally.

why are you persecuting me?

The Lord was rebuking Saul in the form of a question. It can be translated "You are persecuting me!" (See: rc://en/ta/man/translate/figs-rquestion)