# as his custom was

"as his habit was" or "as his common practice was." Paul usually went to the synagogue on the Sabbath when Jews would be present.

# for three Sabbath days

"on each Sabbath day for three weeks"

# reasoned with them from the scriptures

Paul explained what the scriptures means in order to prove to the Jews that Jesus is the Messiah. (See: [[rc://en/ta/man/translate/figs-explicit]])

# reasoned with them

"gave them reasons" or "debated with them" or "discussed with them"