Matthew 27:45-46,50-51
From the sixth hour (noon) until the ninth hour (3:00 pm) darkness came over all the land. --
This is when the sun refused to shine.
About the ninth hour Jesus cried out in a loud voice, "Eloi, Eloi, lama sabachthani?" which is translated as, "My God, my God, why have You forsaken me." --
This is when Jesus bore our sin-nature. He was born with a true human nature, but without the sin; here is when He "became sin for us." God is too pure to even look upon sin, and He had to turn His back on Jesus. The sun would not honor the execution of God who created it by shining on this spectacle.
And when Jesus had cried out again in a loud voice, He gave up His spirit. --
He died.
At that moment --
At Jesus' death.
The curtain of the Temple was torn in two from top to bottom. The Earth shook and the rocks split. --
The Earth could not stand the sun not shining, and after three hours it upheavaled. That earthquake is what God used (along with His or angels' hands?) to rip the curtain between the Holy Place and the Most Holy Place where God dwelt. This shows us that, now that Jesus has paid our debt in full, we have direct access to the Throne of God through Jesus; we don't need a priest or any other mediator, Jesus alone is our Mediator and our High Priest. And every believer is a priest under Him in petitioning God on behalf of our fellow man.
Even so, come, Lord Jesus!
