In Romans 15:16 Paul said that he was a minister of Christ Jesus [the Son] to the nations, ministering as a priest the gospel of [the Triune] God, that the offering of the nations might be acceptable, having been sanctified in the Holy Spirit. Paul was a priest of the gospel of the Triune God, ministering Christ Jesus, the Son, to the nations. Eventually, the result of his work was to offer the nations to God as a sanctified entity through the Holy Spirit.
SECOND CORINTHIANS 3:3
In 2 Corinthians 3:3 Paul tells the Corinthians that they are a letter of Christ [the Son] ministered by the apostles, inscribed not with ink but with the Spirit of the living God [the Triune God]. Here again we can see the Divine Trinity in the divine move and in our experience. Eventually, the believers become a letter to communicate the Son, and this letter is written with the Spirit as the ink. This Spirit is the very element of the living God, the Triune God, for writing this letter that conveys Christ.
In John 4:10 the Lord Jesus told the Samaritan woman, "If you knew the gift of God, and who it is that says to you, Give Me a drink, you would have asked Him, and He would have given you living water." In this verse we see the gift of God [God the Father] and the Son as the Giver of the living water [the Spirit]. Even in such a short verse we can see the Three of the Divine Trinity. The Father is the Possessor of the gift, the Son is the Giver of the gift, and the Spirit is the gift. The entire New Testament speaks concerning the Divine Trinity with different expressions and from different angles.
FIRST JOHN 5:6-9
In 1 John 5:6-9 we are told that the Spirit, as the truth, testifies (v. 6) that the testimony of God [the Father] is greater than the testimony of men (v. 9a) and that God has testified concerning His Son (v. 9b). All Three of the Divine Trinity are involved in this testifying. The Spirit testifies, His testifying is the Father’s testimony, and the Father’s testimony is concerning the Son.
Revelation 4:2—5:6 is a record of a universal scene. In this scene, there is God [the Triune God] sitting on the throne (4:2), the seven Spirits of God and the seven lamps of fire burning before the throne of God (4:5), and the Lamb standing in the midst of the throne and of the living creatures and elders (5:6). The throne of the Triune God is the center. In front of this throne are seven burning lamps, which are the seven Spirits of God. In the midst of the throne and of the four living creatures and in the midst of the elders is a Lamb standing. The Father, the Son, and the Spirit are moving in this scene to carry out the eternal economy of the Triune God. His economy was a mystery. No one in the universe was qualified to open this mystery except the slain Lamb. He has the qualifications and the standing to open the scroll, to open the mystery of the universe, the mystery of God’s economy.
(Living In and With the Divine Trinity, Chapter 7, by Witness Lee)