In the beginning was the Word, and the Word was with God, and the Word was God. (John 1:1, NASB)
There are many places within the Bible that refer to Jesus as God, but this is the one that I quote most often. In the beginning was the Word. The Word is explained in Thayer’s Lexicon as it is used in John. “…denotes the essential Word of God, Jesus Christ, the personal wisdom and power in union with God, his minister in creation and government of the universe, the cause of all the world's life both physical and ethical, which for the procurement of man's salvation put on human nature in the person of Jesus the Messiah, the second person in the Godhead, and shone forth conspicuously from His words and deeds.” (See lexicon at BlueLetterBible.org).
John is saying that the Word was with God. To be with something, there must be at least two separate items. John also says that the Word was God. How can Jesus be separate from God, yet still be God? First of all, He is God. I say that because as humans, we have a tendency to place our human limitations upon God. Second, Jesus is the second person in the Godhead.
One example of God’s amazing ability is the fact that God is perfect and cannot forget anything; however, He says that He will forget our sins if we repent. How can God forget anything? He doesn’t forget because He has a bad memory, He forgets because He chooses to remember them no longer. God has abilities that are beyond our human comprehension.
I can’t explain how God does it, but through His word it is clear that the Father, Son and Holy Spirit are one. Many people ask, “If Jesus is God, who He was talking to while on the cross or praying in the garden? The answer is that He was talking to the Father. Jesus is God but He is not the Father. In the same sense, Jesus is not the Holy Spirit. This can be said for all three; the Father is not the Holy Spirit and the Holy Spirit is not the Father. They are all three separate identities that make up the One God. This is what John is saying, Jesus is with God and He is God.
God has power and abilities that are beyond our human limitations and that gives me the confidence to know that we have placed our faith in a God that is more powerful than we are. I would have great fear if my God could only do the things that I had the ability to do myself. God is all powerful and all-knowing and He is not limited to our understanding of Him.