Does the word "spirit" in "The Lord God has sent me, and His spirit" (Isaiah 48:16) refer to what Christians call the "third member of the trinity"? Let's find out.
Christian commentators who are looking for trinitarian allusions in the Jewish Scriptures translate part of Isaiah 48:16 as, "The Lord God and His Spirit have sent me." However, a proper rendering of the verse reads: "And now the Lord God has sent me, and His spirit." The last two Hebrew words in this verse are shelachani ve-rucho ("He has sent me, and His spirit"), with "me, and His spirit" being the direct objects of "sent." Even though a definite direct object is usually preceded by the participle 'et, this grammatical rule is frequently not observed in the Bible, e.g., Exodus 15:9; Judges 5:12; Psalms 9:5, 20:3-4, 45:4. In fact, 'et rarely occurs in the poetic parts of the Bible. Thus, the meaning of the verse is that God has sent Isaiah accompanied by His prophetic spirit. There is no mention of the third member of the Trinity doctrine. Instead, Isaiah affirms that God, who has placed within him the power of prophecy, sent him.
The spirit is always at the disposal of God to bestow upon whomever He chooses, as stated in Numbers 11:17, 25, 29; Isaiah 42:1, 44:3; Joel 3:1. If this spirit referred to the third member of a coequal tri-unity god, how could it be ordered about at the discretion of the other members of this group? We see that the Jewish Scriptures teach that "spirit" does not refer to the third person of a tri-unity god. Thus God says to Moses, "And I will take of the spirit which is upon you, and I will put it upon them. . . . And He took of the spirit which was upon him, and He put it upon the seventy men, the elders, and it came to pass, when the spirit rested upon them, that they prophesied. . . . And Moses said . . . 'would that all the Lord's people were prophets, that the Lord would put His spirit upon them'" (Numbers 1:17, 25, 29).
Such a condition makes it obviously impossible to consider the spirit as being an associate of God, let alone coequal with Him.