Charles Ellicott Commentary Acts 9:20

"And straightway in the synagogues he proclaimed Jesus, that he is the Son of God." — Acts 9:20 (ASV)

And immediately he preached Christ in the synagogues.—The word “immediately,” as interpreted by the inference drawn in the previous Note, must be understood to refer to the Apostle’s first public appearance in the synagogues of Damascus after his return from Arabia. The tense of the verb implies that the work was continued for some length of time.

What he had to proclaim was, first, that the Christ was actually and truly the Son of God, just as much as the Son of David; and, secondly, that Jesus of Nazareth had been shown to be the Christ. The better manuscripts, however, give the reading, preached Jesus.

We may assume the line of reasoning was identical to that of Acts 13:16-41.

It is also interesting to remember that the Samaritans had their own synagogue in Damascus, and that he may therefore have preached to them, thereby following in Philip's footsteps and taking his first step in the great work of breaking down the barriers that divided Israel from the world.