I don’t believe the Holy Spirit will mind that we’re only devoting one article to Him in this series. He is sometimes called the shy member of the Trinity, after all – shy, not because He is timid, but because it’s His joy and ministry to draw attention to Christ (Joh 15:26; 16:14).
A certain shyness on our part is appropriate when speaking about the Spirit. As Bernard Ramm says, “To profess to know a great deal about the Spirit of God is contrary to the nature of the Spirit of God. There is a hiddenness to the Spirit that cannot be uncovered … a reticence of the Spirit that cannot be converted into openness. For these reasons one feels helpless, inadequate, and unworthy to write a line about the Spirit.”
There is at least one place, however, where the apostle Paul speaks about the Holy Spirit with profound boldness. In a moment of “apostolic audacity,” with courage the Spirit alone could supply, Paul writes that “the Lord is the Spirit, and where the Spirit of the Lord is, there is freedom. … For this comes from the Lord who is the Spirit” (2Co 3:17-18). In this statement, the inspired author makes two declarations regarding the Spirit that have tremendous relevance for the doctrine of the Trinity.
First, He Identifies the Holy Spirit As God
Here’s some context. Paul has just finished quoting the Greek translation of Exodus 34:34: “But when one turns to the Lord, the veil is removed” (2Co 3:16). In Exodus 34, Moses’ face shone as he came down from Mount Sinai “because he had been talking with God” (v29). Out and about with the Israelites, Moses would cover his face with a veil. But whenever he turned back to see God, off came the veil, and Moses would contemplate the glory of God with an unveiled face (vv33-34).
As Exodus makes clear, this was a recurring experience: “Now Moses used to take the tent and pitch it outside the camp” (33:7). And “when Moses entered the tent, the pillar of cloud would descend and stand at the entrance of the tent …. Thus the LORD used to speak to Moses face to face” (33:9-11). And “whenever Moses went in before the LORD to speak with him, he would remove the veil, until he came out” (34:34).
The word “LORD” is in capital letters. See how boldly Paul speaks about the Holy Spirit? He’s saying that the LORD Moses kept turning back to see is the Holy Spirit. Yahweh is the Spirit!
Of course, in identifying the Spirit as Yahweh, Paul is identifying the Spirit as God. And to do this Paul does not need to run roughshod over his OT text. The Exodus verses we’ve already quoted record that it was when the pillar of cloud descended that the LORD would speak, thus connecting the cloud with Yahweh. In other words, Paul is not reading NT realities back into the text that were never there in the first place. “The Lord whom Moses met at the tent of meeting was already the Spirit, the same Spirit whom Paul’s addressees are encountering when they behold ‘the glory of the Lord’ (2 Cor 3:18).”
Second, He Distinguishes the Holy Spirit From God
This series has focused primarily on the Lord Jesus. Time after time, we have worked through texts in which Scripture identifies Jesus as God and, in the same breath, distinguishes Him from God. In doing this, Scripture pressures us to confess the doctrine of the Trinity. Well, now we are looking at a text that repeats this phenomenon for the Holy Spirit. No sooner does Paul identify Him as Yahweh than he distinguishes Him from Yahweh: “Now the Lord is the Spirit, and where the Spirit of the Lord is, there is freedom” (v17). The Lord is the Spirit, and the Spirit is the Spirit of the Lord.
Once again, Scripture is speaking of God in two different registers. The Spirit is Yahweh, and He is the Spirit of Yahweh at the same time! There’s still only one Yahweh, but that the Spirit is Yahweh cannot be predicated of the Spirit alone, for it is equally true of the Father and of the Son. Thus, there is a oneness of God in terms of essence, but a threeness of God in terms of Persons – one God in three Persons.
Corroboration From the Rest of the NT
When we turn to the rest of the NT we find more of the same. For starters, Scripture affirms the Spirit’s personhood.  The Spirit is not merely a force. He speaks in the first person (Act 13:2), thinks like a person (Rom 8:27), and comforts like the person of Christ (Joh 14:16). He performs other actions attributed to persons, such as leading (Rom 8:14), witnessing (v16), interceding (v26) and grieving (Eph 4:30). This corroborates the second half of 2 Corinthians 3:17 – that the Spirit is distinguished from God as a distinct Person.
But second, the NT confirms the first part of our verse – that He is a divine Person. The facts that the Spirit can be blasphemed (Mat 12:28-31), possesses divine attributes such as omniscience (1Co 2:10), and is spoken of in parallel with God (Act 5:1-11) all argue for the deity of the Spirit. Both truths, His deity and personhood, come together in the way the Bible pairs His name. Baptism, for example, is in the “name of the Father and of the Son and of the Holy Spirit” (Mat 28:19). How strange if the first two persons were deity but the third an angel (as Islam teaches). “In the light of Jesus’ words, the biblical reality is that to name the Holy Spirit is to name God truly but not exhaustively. The Holy Spirit is as much deity as is the Father as is the Son, but distinct as a person from both.”
The doctrine of the Trinity is therefore seen to be scriptural, not only by looking at the Son but also by looking at the Holy Spirit.
 Quoted in Graham A. Cole, He Who Gives Life: The Doctrine of the Holy Spirit (Wheaton, IL: Crossway, 2007), 42.
 Mark A. Seifrid, The Second Letter to the Corinthians (Grand Rapids, MI: Eerdmans, 2014), 162.
 Bible quotations in this article are from the ESV.
 David Gooding, “The Trinity: God’s Revelation of Himself” (Belfast: Myrtlefield Trust, 2018), 38-40.
 Wesley Hill, Paul and the Trinity: Persons, Relations, and the Pauline Letters (Grand Rapids, MI: Eerdmans, 2015), 153. Original emphasis.
 For this and the following paragraph, see Cole, He Who Gives Life, 65-72.
 Cole, 70.