The priests request the ability to question Abinadi. Undoubtedly, the king could imprison Abinadi forever, and perhaps execute him, without any reason more than what the people had suggested. However, the priests desire to question him. This suggests that the rejection of Abinadi’s message was not universal. Indeed, the numbers of people who later follow Alma suggest that there was sympathy to his message.
The trial would allow the priests to paint him in a different light. They were apparently certain that they could entrap him with religious blasphemy, and that would be a point that could be used to quash any support that Abinadi’s preaching might have had.
Thus, they bring him to court. What we get in verse 19 is Mormon’s foreshadowing of what will happen. He will show it to us in dialogue, but lest we miss it, he will show Abinadi getting the upper hand in all of the arguments.