Scripture repeatedly tells us no one has seen God the Father at any time. The Apostle John makes this quite clear: “No one has seen God at any time. The only begotten Son, who is in the bosom of the Father, He has declared Him” (John 1:18).
John also repeats this same statement in his first epistle: “No one has seen God at any time” (1 John 4:12). John chapter 1 tells us the Apostle was a personal eyewitness of “the Word” who became flesh as Jesus Christ. Therefore the “God” whom no one has ever seen at any time has to be referring to the Father.
We also see two explicit statements from Jesus Christ Himself stating the same thing: “And the Father Himself, who sent Me, has testified of Me. You have neither heard His voice at any time, nor seen His form” (John 5:37). And in John 6:46 Jesus again emphasises: “No one has seen the Father except the one who is from God; only he has seen the Father.”
The existence of the One whom Christ referred to as ‘the Father’ was not well understood before Christ’s coming. John’s statement that Jesus Christ “declared” the Father can also be translated as “made him known” (New International Version, English Standard Version, New Revised Standard Version) or “reveal[ed] Him” (Green’s Literal Translation).
However in the Old Testament period we are told a number of people did see God. They include:
The “God” who appeared and spoke with these individuals is identified as “God” (Elohim), “the LORD” (YHWH or Yahweh), “the God of Israel,” “the God of your fathers,” “the God of Abraham, the God of Isaac, and the God of Jacob,” “God Almighty” (El Shaddai), “I AM WHO I AM” and “I AM.”
In Exodus 3:13-14, when God appeared to Moses at the burning bush to tell him he would deliver the Israelites out of their Egyptian slavery Moses asked Him “...‘Indeed, when I come to the children of Israel and say to them, “The God of your fathers has sent me to you,” and they say to me, “What is His name?” what shall I say to them?’ And God said to Moses, ‘I AM WHO I AM.’ And He said, ‘Thus you shall say to the children of Israel, “I AM has sent me to you.”’
Fifteen centuries later Jesus confirmed he was that same Being: "Jesus said to them, ‘Most assuredly, I say to you, before Abraham was, I AM.’...” then they took up stones to throw at Him.” (John 8:58-59). The Jews who heard Jesus say these words knew exactly what Jesus meant—that He was claiming to be the “I AM” who had interacted with Moses, and they immediately tried to stone Him to death for claiming to be God.
In 1 Corinthians 10:1-4 Paul clearly tells us the God who accompanied Israel during the Exodus was the Being who became Jesus Christ: "Moreover, brothers, I would not that you should be ignorant, how that all our fathers were under the cloud... and did all eat the same spiritual meat; and did all drink the same spiritual drink: for they drank of that spiritual Rock that followed them: and that Rock was Christ.”
Paul used the unusual term “Rock” to apply to Jesus Christ as he was pointing to the miracle of water coming from the rock (Numbers 20:11), and Moses had also referenced God as “the Rock” in Deuteronomy chapter 32 in verses 4, 15, 18 and 30-31.
The Bible shows Jesus was the One who interacted with the patriarchs, prophets and the people of Israel as the LORD or God on behalf of the Father. He identifies Himself as ‘I AM’ and ‘the LORD God... of Abraham.... of Isaac, and... of Jacob’ (Exodus 3:14-15, John 8:58). Therefore the One the Israelites knew as God, who delivered them from Egypt and accompanied them in the wilderness, was known in the New Testament as Jesus Christ (1 Corinthians 10:4).