The Pharisees heard that Jesus had silenced the Sadduccees. They thought they could be like Socrates. They thought that by using clever questions, they could silence the Lord. “Teacher,” they say. They are ready to hit Him. They’re locked and loaded. It’s sort of like when someone begins to say something to you, and, You know you’re about to get it.
“Teacher, which is the great commandment in the Law?” It’s not quite so loaded a question as, “When did you stop mistreating your pets?”
At best, they meant something like: “Which precept or statute of God is most important; which is most central? And then they would discuss it.