What does Mark 12:13 mean?

Jesus and the disciples are in the courtyard of the temple. The temple sits near the west edge of the flat-topped Temple Mount, slightly north of center. Around the temple is the Court of the Gentiles, where God-following Gentiles may pray. Along the edges of the Temple Mount are porticoes where teachers can sit out of the sun and teach. The largest, Solomon's Portico, lines the south edge. Jesus is probably in one of these porticoes. It's common for teachers and philosophers to debate theological and ethical interpretations here.

What's not usual is for these debates to be motivated by the desire to have one's opponent killed. The actions of Jesus' critics here are not merely rhetoric; they have murderous political intention.

Luke 20:19–20 adds more detail. The scribes and chief priests want a valid excuse to arrest Jesus there and then, so they send the Pharisees and Herodians to try to trap Jesus into saying something that would incriminate Himself. "Trap" is from the Greek root word agreuo and literally means to hunt; the word implies an intent to capture by surprise. Matthew's account uses "entangle" which is from the Greek root word pagideuo: "to ensnare, as a bird in a net" (Matthew 22:15).

The Pharisees, obsessed with the law, will determine if Jesus encourages behavior that contradicts the tenants of Judaism. The Herodians—Jews who support the Rome-empowered kings and tetrarchs—are on the look-out for any seditious intent in Jesus' words. The priests, scribes, and Pharisees are invested in a tradition-bound version of Jewish culture; the Herodians prefer the Greek culture and Roman rule. In Jesus, they've had a common enemy for several years (Mark 3:6).