What does Mark 12:28 mean?
It's normal for religious leaders to come to the temple courtyard and debate each other about theology. However, the challenges against Jesus are more than intellectual exercises. The chief priests, Sadducees, Pharisees, scribes, and Herodians all see Jesus as a threat, either to their social status or to the relative peace with Rome. So, the questions the religious and civil leaders are asking Jesus are intended to get Him to say something either sacrilegious or seditious. They want Him dead, but they need reasons adequate to involve higher authorities.Sadducees, Herodians, and Pharisees have failed, so now it is a scribe's turn. The office of scribe is an ancient and honorable one. They originally kept records for rulers (1 Chronicles 24:6; Ezra 4:8; Esther 3:12). By the time of Jesus, they were primarily known as experts in the Mosaic law (Ezra 7:11). Ideally, they provide wise counsel on difficult matters (1 Chronicles 27:32).
Unfortunately, as in any profession, some are not so honorable. Jeremiah spoke of the "lying pen of the scribes" (Jeremiah 8:8) and Nahum described them as unfaithful as a cloud of locusts whose presence depended on the weather (Nahum 3:17).
Throughout Israel's history, the people wavered between following God and worshiping idols. At times, the kings and priests didn't even know where the copy of the Mosaic law was. When the people disobeyed the Law, God punished them. Eventually, the scribes grew so fearful of God's punishment that they created interpretations of the Law that went above and beyond what God had intended. For example, while God said to do "no work" on the Sabbath, the scribes added so much manmade detail that modern Jews following their teachings won't press buttons on such days.
The scribes claim these are "oral laws" which God gave to Moses on Mount Sinai but Moses didn't record in writing. The Pharisees love these laws almost as much as they love enforcing them on the laypeople (Matthew 23:4). Jesus calls them manmade traditions (Mark 7:1–13) and condemns anyone who makes people feel shame for not doing what God didn't intend.
And so now, the Pharisees have sent a scribe to test Jesus (Matthew 22:34–35). Jesus has been teaching with authority His entire ministry (Mark 1:27). If they can win a debate against Him in front of this crowd in Jerusalem, He will lose credibility and prove to not be such a threat to their religious authority. They fail to understand that no one knows God's law as well as God's Son does.