In line 29, the Creed, having plainly set forth the doctrine of the Trinity; shifts to proper Christology. It warns that those who reject the doctrine of the Incarnation—that is, the doctrine as it was handed down from the Apostles, as we find it in the Scriptures—cannot be saved.

Line 30 begins a thorough articulation of what it means to believe in the incarnation
of our Lord Jesus Christ faithfully. At its most basic level, it means to confess the two natures of Christ.

Lesson from the Creed

Now this is the true faith:

That we believe and confess
that our Lord Jesus Christ, God’s Son,
is both God and human, equally.

Athanasian Creed, line 30

Explanation from Scripture

John 1:1, 14 and Colossians 2:9 give us the clearest expression in Scripture of the two natures of Christ: that He is not only God’s Son, but true God and true Man, at once. In the beginning was the Word, and the Word was with God, and the Word was God … And the Word became flesh and dwelt among us, and we beheld His glory, the glory as of the only begotten of the Father, full of grace and truth (John‬ ‭1‬:‭1‬, ‭14‬ ‭NKJV‬‬). And: For in Him dwells all the fullness of the Godhead bodily (Colossians‬ ‭2‬:‭9‬ ‭NKJV‬‬).

If these were all we had, we could still be assured that Christ is at once both true God and true Man.

But there’s more! For example, Philippians 2:5-11:

Let this mind be in you which was also in Christ Jesus, who, being in the form of God, did not consider it robbery to be equal with God, but made Himself of no reputation, taking the form of a bondservant, and coming in the likeness of men. And being found in appearance as a man, He humbled Himself and became obedient to the point of death, even the death of the cross. Therefore God also has highly exalted Him and given Him the name which is above every name, that at the name of Jesus every knee should bow, of those in heaven, and of those on earth, and of those under the earth, and that every tongue should confess that Jesus Christ is Lord, to the glory of God the Father.

Philippians‬ ‭2‬:‭5‬-‭11‬ ‭NKJV‬‬

Two things here: First, when it says He was in the form of God, and equal with God; this means the Son shares in all the divine attributes; and is equal with the Father and the Spirit. Second, when it says He was found in appearance as a man; this doesn’t mean He only appeared human. Rather, it means that when you looked at Him, there was nothing about His appearance that indicated His divinity. As it was foretold in Isaiah 53:2: There was nothing beautiful or majestic about his appearance, nothing to attract us to him (NLT‬‬). So this passage establishes—as a third witness—both the divinity and the humanity of Christ.

But notice also St. Paul’s warning to the churches of Ephesus: Therefore take heed to yourselves and to all the flock, among which the Holy Spirit has made you overseers, to shepherd the church of God which He purchased with His own blood (Acts‬ ‭20‬:‭28‬ ‭NKJV‬‬). How could God—who is a Spirit (John 4:24)—shed His own blood? Only if He were to dwell bodily, as in Christ Jesus.

We also have an abundance of Scripture that bears witness to His divinity here, and His humanity there; so that we must confess, as the Creed says, that our Lord Jesus Christ, God’s Son, is both God and human, equally.

Scriptures that proclaim Christ as God

For unto us a Child is born, Unto us a Son is given; And the government will be upon His shoulder. And His name will be called Wonderful, Counselor, Mighty God, Everlasting Father, Prince of Peace. (Isaiah‬ ‭9‬:‭6‬ ‭NKJV‬‬)

“‘Behold, the virgin shall be with child, and bear a Son, and they shall call His name Immanuel,’ which is translated, ‘God with us.’” (Matthew‬ ‭1‬:‭23‬ ‭NKJV‬‬)

Jesus said to them, “Most assuredly, I say to you, before Abraham was, I AM.” (John‬ ‭8‬:‭58‬ ‭NKJV‬‬) Jesus is here claiming to be Yahweh—the LORD—who revealed Himself to Moses saying: “I AM WHO I AM.” And He said, “Thus you shall say to the children of Israel, ‘I AM has sent me to you’” (Exodus‬ ‭3‬:‭14‬ ‭NKJV‬‬)

And now, O Father, glorify Me together with Yourself, with the glory which I had with You before the world was (John‬ ‭17‬:‭5‬ ‭NKJV‬‬). Christ is claiming equal, shared glory with God the Father, from eternity.

This list is hardly exhaustive. See also John 20:28; Romans 9:5; and 1 Timothy 3:16.

Scriptures that proclaim Christ’s humanity

Therefore let it be known to you, brethren, that through this Man is preached to you the forgiveness of sins (Acts‬ ‭13‬:‭38‬ ‭NKJV‬‬).

… because He has appointed a day on which He will judge the world in righteousness by the Man whom He has ordained. He has given assurance of this to all by raising Him from the dead (Acts‬ ‭17‬:‭31‬ ‭NKJV‬‬).

For there is one God and one Mediator between God and men, the Man Christ Jesus (1 Timothy‬ ‭2‬:‭5‬ ‭NKJV‬‬).

And these are just such Scriptures as patently state Christ’s humanity; yes—even in His resurrection and ascension! He is still the Man Christ Jesus; and shall return to judge the world as a Man.

But obviously other passages confirm His true humanity by certain proofs. For instance, that He had a mother (Galatians 4:4); as well as any passages that tell us He was hungry or ate; that He was weary and slept; that He was moved with emotion and wept; that He was touched; that He sweated; and certainly, that He bled and died—these are all proofs of His humanity! For none of those are true of God as God.

Thus, again we conclude, as we always have: Christians do not believe, confess, and teach any of this simply because it is in a Creed. Rather, Scripture commands us to: Test all things; hold fast what is good (1 Thessalonians‬ ‭5‬:‭21‬ ‭NKJV‬‬). The Athanasian Creed has been tested for centuries, and found good. For it boldly and plainly summarizes the faith which was once for all delivered to the saints (Jude‬ ‭1‬:‭3‬ ‭NKJV‬‬), as it pertains to the doctrine of the Trinity, and the doctrine of Christ.