While orthodox Christianity holds firmly to the Doctrine of the Trinity as an essential Christian teaching, there are those who deny it outright. Unitarians claim to hold to a strict monotheism, denying Jesus to be God himself; Jews hold to the belief that God is one as articulated in Deuteronomy 6:4. With this denial of this doctrine, there is usually the argument that the Old Testament does not teach this. This statement must be tested and weighed as to its validity. Therefore, I want to look at the text of Isaiah 48:12-17. In verses 12 and 13 the Lord introduces Himself as the self-existent God (“I am he”), the eternal God (“I am the first and I am the last”), the Almighty and Sovereign Creator of everything (verse 13).
These two verses point to the same God described throughout the Old Testament. In Deuteronomy 32:39 He says of Himself I, even I, am he, and there is no god beside me. Jumping to verse 16 we see some of His attributes that He reveals. Firstly, He does not keep dark secrets. He reveals His truth for all to pay attention (“from the beginning I have not spoken in secret”). Secondly, He is eternal (“from the beginning”; “from the time it came to be I have been there”). Then we read a most interesting claim: And now the Lord GOD has sent me, and his Spirit (verse 16c). God was sent by “the Lord GOD” and his “Spirit“. This clearly indicates a distinction between 3 separate role players:
- the Lord currently speaking
- the Lord GOD
- the Spirit of the Lord GOD
We find this interplay between the three role players in the Godhead in Isaiah 61:1:
The Spirit of the Lord GOD is upon me, because the LORD has anointed me to bring good news to the poor; he has sent me …
It is unmistakable from the passage in Isaiah 48 that although God is One, there are three distinct Persons. They are of the same essence, therefore not violating the Scriptural principle of the Oneness of God.
While the Doctrine of the Trinity is understood more clearly from the New Testament, it is a doctrine that is most definitely taught in the Old Testament. From the New Testament the identity of the Father, Son, and the Holy Spirit is made clear, while building on the teachings of the Old Testament in this regard. Unitarians, Jehovah’s Witnesses and Orthodox Jews will find it difficult to deny the evidence of Isaiah 48 that clearly teaches a One God distinguished in three Persons.