The tearing of the curtain would have been extremely shocking to the Jews. The curtain represented Moses, law, covenant and priesthood.
Moses mediated the first covenant at Mt. Sinai.
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Now when all the people perceived the thunderings and the lightnings and the sound of the trumpet and the mountain smoking, the people were afraid and trembled; and they stood afar off, and said to Moses, "You speak to us, and we will hear; but let not God speak to us, lest we die." And Moses said to the people, “Do not fear; for God has come to prove you, and that the fear of him may be before your eyes, that you may not sin.” And the people stood afar off, while Moses drew near to the thick darkness where God was. (Exodus 20:18-21)
The people would not approach God. Only Moses approached God. There was separation between God and man. The successors to Moses, the Levitical Priests, were the only one’s allowed to approach God behind the curtain. Jesus even calls the priests “those who sit on Moses’ chair.”
The tearing of the curtain meant an end to the mediation of Moses and his successors the Temple Priests. It meant an end to Temple worship. It meant an end to the covenant which Moses had mediated.
The curtain didn’t just rip but was torn - forcibly rend. God had violently removed it the priesthood from the temple priests under the old covenant and established his new priesthood under a new covenant. Remember that covenants only end when one person in the covenant dies. The old covenant was between God and Israel and God had just died on the cross - that is the moment the curtain was rend in two, right when Jesus breathed his last.
The tearing of the curtain would have been shocking to the Jews and those who heard of it would have understood clearly what it meant because they undestood the actions of Moses at Mt. Sinai, the covenant, and what the curtain represented - covenant, law, mediation and preisthood. All of it was violently taken away at that moment, the moment Jesus died and the covenant ended.
-Tim-