When the New Testament was written, they also applied the word Lord to Christ. This gave the inference that the “Lord” of the Old Testament was the same “Lord” of the New Testament. In other words, they thought Jesus was the Jehovah of the Old Testament. However, there are enough scriptures to denote otherwise. For example, Luke wrote:
The God of Abraham, and of Isaac, and of Jacob, the God our fathers, hath glorified His Son Jesus; whom ye delivered up, and denied him …. (Acts 3:13)
The God of our fathers raised up Jesus, whom ye slew and hanged on a tree. (Acts 5:30)
Paul the Apostle clarifies it further by saying:
God, who at sundry times and in divers manners spake in time past unto the fathers by the prophets, hath in these last days spoken unto us by the Son …. (Heb. 1:1-2)
And notice who spoke to Moses:
And God spake unto Moses, saying: Behold, I am the Lord God Almighty, and Endless is my name; for I am without beginning of days or end of years; and is not this endless?
And I have a work for thee, Moses, my son; and thou art in the similitude of mine only Begotten; and mine Only Begotten is and shall be the Savior, for he is full of grace and truth; but there is no God beside me, and all things are present with me, for I know them all. (Moses 1:3, 6)
So it was God the Father that spoke to Moses and revealed:
And I, God, created man in mine own image, in the image of mine Only Begotten created I him; male and female created I them. (Moses 2:27)
And I, God, saw everything that I had made, and, behold, all things which I had made were very good …. (Moses 2:31)
Here the Father is admitting that He created man and everything was pronounced good. These scriptures, then, indicate that (1) the Father was the Creator; (2) He was the one who spoke to Moses giving him the law and commandments; and so (3) He was the Jehovah of the Old Testament.
When the brother of Jared prayed for the Lord to touch the stones so they would shine in the darkness, he saw the finger of Jesus, and then he saw His whole form, which was the body of His spirit. Jesus then said, “Never have I showed myself unto man ….” (Ether 3:15) We may ask, then, who was it that appeared to those ancient prophets prior to this time? It must have been God the Father, the Jehovah of the Old Testament.
We see that the God of Abraham, Isaac, and Jacob in the Old Testament spake in the New Testament through His Son. In both testaments it was the same God who was speaking and revealing His will to man.
If Jesus were the Jehovah of the Old Testament, then the Israelites were worshipping Him. But while Christ was on earth, He never required His disciples to worship Him, but rather to worship the Father. Why would Jesus be the God of the Old Testament but not of the New Testament? But if the Father was the God of the Old Testament, then it stands to reason why Jesus referred to Him about 170 times and directed all to worship Him in the New Testament.