28Then one of the scribes came, and having heard them reasoning together, perceiving that He had answered them well, asked Him, "Which is the first commandment of all?"
29Jesus answered him, "The first of all the commandments is: 'Hear, O Israel, the LORD our God, the LORD is one. 30And you shall love the LORD your God with all your heart, with all your soul, with all your mind, and with all your strength.' This is the first commandment. 31And the second, like it, is this: 'You shall love your neighbor as yourself.' There is no other commandment greater than these."
32So the scribe said to Him, "Well said, Teacher. You have spoken the truth, for there is one God, and there is no other but He. 33And to love Him with all the heart, with all the understanding, with all the soul, and with all the strength, and to love one's neighbor as oneself, is more than all the whole burnt offerings and sacrifices."
34Now when Jesus saw that he answered wisely, He said to him, "You are not far from the kingdom of God."
But after that no one dared question Him.
At this point in time, there are so many commandments, rules, and laws put in place that it may have seemed almost impossible to correctly follow God's wishes. As they were probably in trouble when breaking any of the laws, the desire to know which are the most important commandments was probably a very real desire. Jesus was able to explain that all of God's wishes could be fulfilled by following these two commandments. All other commandments and laws were probably put into place as a means to try to follow these two commandments.
The series of questions is starting to take on a different tone. In the first question, they flat out challenged Jesus' authority. In the second question, the Pharisees tried to trap Jesus with the question on paying taxes. In the third question, the Sadducees simply asked the question they felt had no answer. This fourth question seemed to simply be a question from someone searching for a truth.
As the tone of the questions changed, so has the tone of the answers as well as the reactions of the ones asking the questions. In the first question, they didn't even comprehend the answer and they went away in fear. In the second question even though they expected it to be an easy trap, Jesus gave a very good answer and they marveled at Him. In the third question, Jesus pointed out their misunderstanding. It didn't say what their reaction was to this question, but it says this scribe had heard them reasoning together and felt that Jesus had answered them well. So I feel these Sadducees had learned something here. In this fourth question, the man not only understood the answer, but was able to go a step beyond the answer by saying it could replace even the burnt offerings and sacrifices that were a very big part of their religion. By this statement, the scribe was challenging his religion himself.
With each question and answer, they got closer and closer to understanding the truth. As Jesus said after the last question, he was getting close to the kingdom of God. A key part of the last question that he had not comprehended yet was that the burnt offerings and sacrifices that had been such a big part of their religion is going to be replaced with the sacrifice of Jesus.
I wonder if the fact that no one dared question Him more was because they didn't want to be drawn away from their beliefs any more. They had been trying to trap Jesus to destroy Him. Instead Jesus was drawing them out of their own beliefs and building up His authority and respect.