Here the author begins to give background information about Herod and why he beheaded John the Baptist. (See: [[rc://en/ta/man/translate/writing-background]])
This can be stated in active form. Alternate translation: "Herod sent his soldiers to arrest John and had them bind him in prison" (See: [[rc://en/ta/man/translate/figs-activepassive]])
"the wife of his brother Philip." Herod's brother Philip is not the same Philip who was an evangelist in the book of Acts or the Philip who was one of Jesus' twelve disciples. (See: [[rc://en/ta/man/translate/translate-names]])