For you know the grace of our Lord Jesus Christ, that though he was rich, yet for your sake he became poor, so that you through his poverty might become rich. (2 Corinthians 8:9)This is the connection between Bethlehem and Calvary; the manger and the cross. As God, he is immortal. He could not die. His incarnation was necessary for in God's design of the redemption, someone must be sacrificed for the expiation of sin.
The purpose of his poverty is laid here: "so that by his poverty, we might become rich", implying of course that before the great sacrifice, before we have inherited all the spiritual blessings in Christ (Eph. 1:3), we were in a state of poverty. We were poor in the sense that we are subject to pain and suffering as a result of the sin that entered through one man and spread to all mankind. It is a misery so great that would last for all eternity-- if the Lord had not shown his mercy. But he did showed his mercy by sending his Son to deal with this root problem of all our miseries namely "sin".
The rich and glorious King came not to be served but to serve and give his life as a ransom for many (Mark 10:45). In Him we have redemption through His blood, the forgiveness of sins, according to the riches of His grace." (Eph. 1:7). And because the root problem of sin has been dealt with, we are now rich. Every spiritual blessing is ours. We are already given much benefit today, and more will be given in eternity: "so that by his poverty, we might become rich."