In a football, match when a player is unable to continue, a substitute is found.
Without a substitute the team would find it hard to continue the game. The substitute plays a vital role.
In the Old Testament when the people of Israel were aware of their own inability to continue because of sin in their lives they used a substitute - a lamb. The lamb was slain on the altar and offered as a sacrifice for their sin.
But year after year it was necessary for the high priest to make the sacrifice to cover the sin of the people.
The Bible says that our sin needs to be dealt with.
Without a substitute we would have to pay the price ourselves. But who would die as my substitute? Would you? Who would die as yours? Would I?
But God in His infinite wisdom, grace and mercy has provided our substitute, His own Son - Jesus!

When John the Baptist saw Jesus he said: "Behold the Lamb of God, which taketh away the sin of the world." (John 1 v29).
Jesus went to the cross at Calvary to die. "..He is brought as a Lamb to the slaughter.." (Isaiah 53 v7).
Christ died in our place, as our sacrifice. "For Christ also hath once suffered for sins, the Just for the unjust, that He might bring us to God." (1 Peter 3 v18).
Yes! Jesus, the divinely-appointed substitute, has played that eternally vital role for you and me!
Jesus "was delivered for our offences, and was raised again for our justification." (Romans 4 v25)
Because of His substitution we are justified (cleared from all charges of guilt).
Now all we need to do is accept and receive what Jesus has done for us.
Here is how you could do just that. Pray a prayer like this:

Lord, I know that I have sinned, but that Jesus has died and paid the penalty for my sin. I am truly sorry for my sin and now turn away from it and receive you, Lord Jesus, as my Saviour.
AMEN