Even if they did have a copy, how would they know how to interpret it? For example, what does not eating milk and meat together mean? At the same meal? Could you take away a meat meal and then immediately have another meal with milk? How long was there to be between the two? Or walls on a roof? How high should they be?Matt 23:1-4--The scribes and Pharisees sit in Moses’ seat. 3So practice and observe everything they tell you. But do not do what they do, for they do not practice what they preach. 4They tie up heavy, burdensome loads and lay them on men’s shoulders, but they themselves are not willing to lift a finger to move them.…
Jesus told His followers to do as the scribes and Pharisees said because they upheld the law with their speech. They were the authorities on the law (seated in the chair of Moses). But they did not uphold it with their actions. They talked the talk, but didn't walk the walk.
I believe that part of the burden Jesus was talking about in this verse had to do with the Jewish traditions, i.e. the traditions of men which Jesus criticized. Men added to God's Word with their traditions and made the law even more complex and burdensome than what God had actually spoken. Also, I believe that the law itself presented a burden which Jesus lifted by fulfilling the law.
I seriously doubt that the average person of that day had a copy of the scriptures. We see in Acts that the Bereans did, but I would imagine that this could have been an exception.
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Many laws also got reinterpreted when culture changed. Thus it was completely allowable when the Sanhedrin agreed not to execute anyone when they wanted to make peace with the Romans. They could set aside the death penalty if they wanted; and they did because it saved countless lives.
I would wager few Christians would know the correct way to interpret "an eye for an eye." The average Jew in Jesus' day apparently did not; and most Christians today don't.