An unspeakably great, unexplorable divine mystery is at the bottom of all this. God’s holiness and righteousness must shut the doors of heaven to us sinners, and He knows that neither we ourselves nor any creature in heaven or on earth can open them for us. He had therefore determined from eternity that what we could not do, He would do Himself, and He would do it in such a way that His divine, wonderful, incomprehensible, and infinite love would be made known to all creatures, to His eternal praise and glory. God had decreed that His dear, only-begotten Son Himself would be sent into the world, that He would become man, that all of our sins would be laid on Him, and that those sins would be completely and eternally blotted out by His deep humiliation and death on a cross.
What happened in Bethlehem was the fulfillment of that eternal decree of the heavenly Father. As soon as His Son became man, the unbearable burden of all humanity’s sin was laid upon Him. And so, as Christ, God’s sacrificial Lamb for the sins of the whole world, lay in a hard crib in the dark stable, the eyes of God looked into the future to see His Son already dying on the cross. Therefore, this atonement for sins, by which God’s offended holiness and righteousness were satisfied and men were reconciled to Him, was already as good as accomplished. For this reason, God immediately opened the gates of heaven as a sign of this glorious event. The heavenly host announced the wonder of His eternal love (which He wants each person to receive) to the humblest of people, the poor shepherds, and when the heavenly choir had concluded its festival hymn of reconciliation with the world, He filled them with joy.
Let us, then, rejoice and be happy today. Let our mouths be full of laughter and our tongues full of praise. For the holy message of Christmas is that heaven’s gates stand open for us.
From God Grant It: Daily Devotions from C.F.W. Walther . Tr. by Gerhard P. Grabenhofer (Concordia Publishing House: 2006), Pages 72-73.