Line 9 of the Creed continues to expand on line 7: What quality the Father has, the Son has, and the Holy Spirit has. That is, all three Persons of the Trinity possess the same divine attributes in perfect measure.

Lesson from the Creed

The Father is immeasurable [or infinite], the Son is immeasurable, the Holy Spirit is immeasurable.

Athanasian Creed, line 9

Explanation from Scripture

The divine attribute of infinity means that God is without limitations. There are essentially two applications of this attribute: immeasurable perfection, and omnipresence.

Herman Bavinck called God a boundless ocean of being. Every perfection of God abounds without measure. Whatever is in God, is infinite: wisdom, knowledge, goodness, power, and the like. Thus, God is omnibenevolent (all-good); He is omniscient (all-knowing, with perfect comprehension); and omnisapient (all-wise).

Likewise, because God is infinite, He is omnipresent. There is nowhere He is not. As the Psalmist declares: If I ascend up into heaven, thou art there: If I make my bed in hell, behold, thou art there (Psalm‬ ‭139‬:‭8‬ ‭KJV‬‬). Likewise, God declares through Jeremiah the prophet: Can a man hide himself in secret places so that I cannot see him? declares the Lord. Do I not fill heaven and earth? declares the Lord (Jeremiah‬ ‭23‬:‭24‬). God indeed fills heaven and earth. If you uncorked a bottle and tossed it into the ocean, the bottle would soon fill, but would not contain the entire ocean! So it is with God and the universe. He fills it, but it does not contain Him; rather, all things are contained in Him. But unlike the bottle in the ocean, the bottle would only contain some of the ocean. But God is equally present everywhere, even though He is contained nowhere.

This attribute of infinity is ascribed in Scripture to the Father, the Son, and the Holy Spirit.

The Father is infinite, for we read: Oh, the depth of the riches and wisdom and knowledge of God! How unsearchable are his judgments and how inscrutable his ways! (Romans‬ ‭11‬:‭33‬). See how the wisdom and knowledge of the Father are without measure and without limit. Likewise, Isaiah 40:28 says, his understanding is unsearchable. Psalm 145:3 says his greatness is unsearchable. And Psalm 147:5 says: Great is our Lord, and abundant in power; his understanding is beyond measure. Thus we see that all of His perfections are without limit.

Likewise, He is everywhere present. When he dedicated the Temple, King Solomon prayed: But will God indeed dwell on the earth? Behold, heaven and the highest heaven cannot contain you; how much less this house that I have built! (1 Kings‬ ‭8‬:‭27‬). Likewise, the Psalmist proclaims: The Lord is high above all nations, and his glory above the heavens! Who is like the Lord our God, who is seated on high, who looks far down on the heavens and the earth? (Psalm‬ ‭113‬:‭4‬-‭6‬)

The Son, likewise, is infinite. For St. Paul speaks of the unsearchable riches of Christ (Ephesians 3:8). Like the Father, the Son is a boundless ocean of perfections. And like the Father, He is everywhere present. For Christ Himself promises His Church: And behold, I am with you always, to the end of the age (Matthew‬ ‭28‬:‭20‬). He is able to be equally present to His saints in every place, because He is the infinite God.

And finally, of the Holy Spirit, King David says: Where shall I go from your Spirit? Or where shall I flee from your presence? (Psalm‬ ‭139‬:‭7‬) The Spirit is everywhere present, with the fullness of God’s perfections—glory and power, knowledge and wisdom, goodness and truth.

Thus we may confirm from Scripture, and therefore must confess, that: What quality the Father has, the Son has, and the Holy Spirit has … The Father is immeasurable, the Son is immeasurable, the Holy Spirit is immeasurable.