The Angel told Joseph, Mary will have a son and you are to name him Jesus for he will save his people from their sins.  In the fullness of time, God sent his son to the earth for a specific purpose.

700 years prior to Jesus birth – the prophet Isaiah wrote about Jesus and what he would experience and do.

“…he was pierced for our rebellion,
crushed for our sins.
   He was beaten so we could be whole.
 He was whipped so we could be healed.
  All of us, like sheep, have strayed away.
  We have left God’s paths to follow our own.
  Yet the Lord laid on him
the sins of us all.”  Is. 53:5-6 NLT 

Unjustly condemned, he was led away…He had done no wrong  and had never deceived anyone.
 But he was buried like a criminal; he was put in a rich man’s grave.  Is. 53:8-9 NLT

When he sees all that is accomplished by his anguish,
he will be satisfied…because of his experience,
 my righteous servant will make it possible  for many to be counted righteous,  for he will bear all their sins.   Is. 53:11 NLT

Christ made it possible for us to be right with God because…

God made him who had no sin to be sin for us, so that in him we might become the righteousness of God.  2 Cor. 5:21 NIV

 We can’t be good enough, moral enough, or religious enough to be righteous before God on our own – that’s why we need Christ

“…I become righteous through faith in Christ. For God’s way of making us right with himself depends on faith.” Phil 3:9 NLT 

God’s grace has saved you because of your faith in Christ. Your salvation doesn’t come from anything you do. It is God’s gift.  It is not based on anything you have done. No one can brag about earning it.  Eph. 2:8-9 NIrV