That God became a man is foundational to the gospel! It's without controversy! If God has not manifested Himself in Christ Jesus, then there is no gospel.
This sublime truth was one of the great foundations of the ancient church. Not only did they believe it, they also sang it. Indeed, the words Paul quotes in this verse are thought by many to be part of one of the ancient songs of the early church. So convinced was the Early Church that Christ Jesus was God, that they often engraved this truth in stone. The following is the translation of an ancient inscription about Jesus, found etched in marble in Asia Minor,
"I am what I was -- God
I was not what I am -- man
I am now both -- God and man."
God was manifest in the flesh in the person of the Lord Jesus! It was not an exalted angel who was manifest, but rather the Almighty God, ruler of heaven and earth. If we reject this central doctrine of the manifestation of God in Christ, then we exclude ourselves from being followers of Christ! To be a follower of Christ is to follow the Christ of the Scriptures--- and the Christ of Scripture is both fully God and fully Man. He has two natures in one person. If we reject this truth, we might have an exceptionally enjoyable religion and call ourselves Christians, but we don't have Biblical Christianity. We have, on this subject, redefined the Biblical Christ in terms that suit us. Not a smart idea!
Listen to this scripture again, "And without controversy great is the mystery of godliness: God was manifest in the flesh." Since repetition is the price of learning, we must stress that this matter of Christ's deity is, for the follower of Christ, without controversy! It is not a doctrine that disciples of Jesus debate! God was manifest in the flesh. As His followers, there are some fundamental things which we have to get straight--- and Christ's deity is one of them.
Matthew Henry says, "He who was manifest in flesh was God, really and truly God, God by nature, and not only so by office, for this makes it to be a mystery. God was manifest in flesh, real flesh. Forasmuch as the children are partakers of flesh and blood, he also himself likewise took part of the same, Hebrews 2:24."
In Christ Jesus, God became a member of the human family. The God who has always been, who has always existed, has now been manifested in Christ Jesus!
As Henry Mahan said, "The Ancient of Days became an infant of days. The Son of the Most-High God became a man of sorrows. He made the World, but as a man, he had no place to lay His head. He who made the rivers asked a woman to give Him a drink of water. He who cast out devils was tempted of the devil, and the author of life died and lay in a tomb."
What immense condescension! He came to earth, was treated as a felon, and put to death. But there, at the cross, the man who was God, was made sin for us (2 Corinthians 5:21). Since the wages of sin is death (Romans 6:23), that man Jesus the God/Man, stepped into our shoes and died in our place. On the third day, however, He rose again thus proving that His sacrifice for our sin was sufficient.
He was hated then and hated now. What say you? Do you love Him or hate Him? If you hate Him, then hate Him with all your might, but if you love Him, pray that you will never be ashamed to declare Him as your God and Saviour. God will certainly answer that prayer.
And that's the Gospel Truth!