In Isaiah 48:16, the speaker, God, distinguishes Himself from two other personalities. He refers to one as the “Lord God,” and to the other as “His Spirit.” Doesn’t this prove that God is a Trinity?
Isaiah 48:16 states: “Come near to Me, hear this: I have not spoken in secret from the beginning; from the time that it was, I was there. And now the Lord God and His Spirit have sent Me.” In the preceding verses, and perhaps in the first part of verse 16, God is the Speaker. However, in the latter part of verse 16, the prophet is the speaker. He speaks of his own divinely appointed mission. Of course, the prophet’s words, in their fullest sense, apply to the Messiah and His mission.
The “Lord God” and the Messiah are two distinct Persons, but why should we think that “His Spirit” is a third Person? Remember, Scripture tells us that man has a spirit (1 Corinthians 2:11; Ecclesiastes 12:7). Is a man’s spirit a person distinct from the man? Of course not! Why, then, should we think that “His Spirit” is a personality distinct from the “Lord God”?
The Spirit of God is consistently presented as the power, spiritual extension, influence, indwelling, and presence of God—not as a third Person within a triune Godhead. This definition applies perfectly to Isaiah’s reference to “His Spirit.”
Isaiah 48:16 provides no support for trinitarian dogma