The second use of be on your guard warns of persecution that was to come upon Christians (see 6:11; 8:34–38; 10:30; see 4:17). They would bring Jewish Christians before local courts of the councils of Jewish leaders, who had authority over Jewish communities (see Matthew 10:17 and possibly Matthew 5:22; see also Acts 4:1–22).
beaten in the synagogues: The apostle Paul's beatings in 2 Corinthians 11:24–25 likely happened in the synagogue.
These trials occurred because they followed Jesus (see Acts 23:24; 24:10–27; 25:1–26:32): Such trials were due to their being followers of Jesus (Mark 13:9, 13). It was not because they actually did something wrong (see 1 Peter 4:14–16).