“And when the sixth hour was come, there was darkness over the whole land until the ninth hour. And at the ninth hour Jesus cried with a loud voice, saying, ‘Eloi, Eloi, lama sabachthani?’ which is, being interpreted, ‘My God, My God, why hast Thou forsaken Me?’ And some of them that stood by, when they heard it, said, ‘Behold, he calleth Elias.’ And one ran and filled a spunge full of vinegar, and put it on a reed, and gave Him to drink, saying, ‘Let alone; let us see whether Elias will come to take him down.’ And Jesus cried with a loud voice, and gave up the ghost. And the veil of the temple was rent in twain from the top to the bottom.
And when the centurion, which stood over against him, saw that he so cried out, and gave up the ghost, he said, Truly this man was the Son of God.”  Mark 15:33-39 (KJB)

For three hours Jesus experienced the darkest time of His life as a Man.  He spent it separated from His Father. Up to this point when He spoke to the Father He always called Him “Father”; in this prayer, an exact quotation from Psalm 22, Jesus calls Him “My God”, asking why He has been forsaken.

Jesus had become sin for us (2 Corinthians 5:21), and had just been judged for the sins of the world.

When Jesus cried and gave up His spirit to the Father we are told that “…the veil of the temple was torn from the top to the bottom”.  That tells us no man tore the veil which separated the Holy place in the temple from the Holy of Holies, the place where the ark of the covenant would be placed had it been present.  The tearing of the veil by God shows that through the death of Jesus all of Adam kind now has access to God and Heaven.

Access to God is only gained through the death, burial, and resurrection of Jesus Christ, the Son of God, God the Son.