Jesus decided the moment of His own death
It was Jesus Himself who decided the moment of His own death. No human being killed Him. Indeed, nobody was capable of killing Jesus. Nobody could take His life from Him by force. He laid it down freely, of His own choice, just as Isaac had been willing to do:
"I am the good shepherd; the good shepherd lays down His life for the sheep.
John 10:11 (NASB)
17"For this reason the Father loves Me, because I lay down My life so that I may take it again. 18"No one has taken it away from Me, but I lay it down on My own initiative. I have authority to lay it down, and I have authority to take it up again. This commandment I received from My Father."
John 10:17-18 (NASB)
The punishment of Jesus in our place makes it possible for God to forgive our sin
We have seen in chapter 9 how the repeated sacrifices of animals in the Temple provided a temporary cover for the sins of the people. However, Jesus' death made it possible for our sin to be fully and permanently forgiven. It could therefore be completely cancelled, removed and disposed of. This solution was achieved once and for all:
24For Christ did not enter a man-made sanctuary that was only a copy of the true one; he entered heaven itself, now to appear for us in God’s presence. 25Nor did he enter heaven to offer himself again and again, the way the high priest enters the Most Holy Place every year with blood that is not his own. 26Then Christ would have had to suffer many times since the creation of the world. But now he has appeared once for all at the end of the ages to do away with sin by the sacrifice of himself. Hebrews 9:24-26 (NIV)
The death of Jesus on our behalf paid our debt to God. That enabled God the Father to cancel the "certificate of debt" because all of our sins had been dealt with by Jesus on the cross:
13When you were dead in your transgressions and the uncircumcision of your flesh, He made you alive together with Him, having forgiven us all our transgressions, 14having cancelled out the certificate of debt consisting of decrees against us, which was hostile to us; and He has taken it out of the way, having nailed it to the cross.
Colossians 2:13-14 (NASB)
Note that last phrase "having nailed it to the cross". This is a reference to the practice in those days when a man was crucified. The executioner would write on a piece of wood the crime or unpaid debt for which the man was being put to death. This served to warn all those passing by about what might happen to them if they were to get involved in the same crime or debt. The point is that on the cross of Jesus no such note was nailed, because He had no crime or debt. The Roman Governor, Pontius Pilate, was well aware of that fact. Therefore he gave orders for the soldiers to nail a sign above Jesus' head which simply said “Jesus of Nazareth, the King of the Jews”. No crime was referred to.
So, what apostle Paul means in the above passage from Colossians, is that it is as if God the Father had nailed our certificate of debt to the cross. It was the debt we owed to Him because of our sin. That is the debt that is nailed to Jesus' cross. That would correspond exactly to how executions were done in those days. It illustrates very clearly how God saw Jesus as paying our debt for us, thus enabling us to be forgiven. The way the prophet Isaiah puts it is that our sins are washed away and we are made as white as snow:
"Come now, and let us reason together,"
Says the LORD,
"Though your sins are as scarlet,
They will be as white as snow;
Though they are red like crimson,
They will be like wool.
Isaiah 1:18 (NASB)
This washing away or cancelling out and forgiving of our sin is possible solely because the guilt of it was placed on Jesus' shoulders. He received all our punishment. Therefore, if we repent and believe, God no longer needs to punish us, because Jesus has taken that punishment in our place, as our substitute:
Therefore there is now no condemnation for those who are in Christ Jesus.
Romans 8:1 (NASB)