Why is it so important to believe Jesus is the Father?

Only the Father could die for our sins. Why? Only the Father is holy and without sin. Because of this, any other sacrifice than the Father Himself could not be acceptable to take away our sins. And only the Father can raise the dead.

How could the Father die for our sins when the Father is Spirit? (Hebrews 2:14-15, 2Corinthians 5:19)

The only way the Father could die for our sins, was for Him to robe Himself in flesh.

His flesh had to be in the form of man. Sin entered into the world by first man Adam. It was necessary that a second man pay the price of blood for this sin.

"For it is not possible that the blood of bulls and of goats should take away sins." - Hebrews 10:4 KJV

"And almost all things are by the law purged with blood; and without shedding of blood is no remission." - Hebrews 9:22 KJV

"Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned: ... For as by one man's disobedience many were made sinners, so by the obedience of one shall many be made righteous." - Romans 5:12, 19 KJV

Jesus said,

"For this is my blood of the new testament, which is shed for many for the remission of sins." - Matthew 26:28 KJV

"Take heed therefore unto yourselves, and to all the flock, over the which the Holy Ghost hath made you overseers, to feed the church of God, which he hath purchased with his own blood." - Acts 20:28 KJV