Read Colossians 1:13-19
Christ existed prior to all creation. He is "the firstborn of every creature" (Col. 1:15). From the original language of the New Testament, this phrase is literally "firstborn of all creation."
The Greek word translated "firstborn" does not mean that He was the first one born; rather, it emphasizes priority and sovereignty. He existed before anything was ever created.
This truth is obvious from verse 16: "For by him were all things created." He had to exist before all created things in order to create them. And because He is the Creator of all things, this implies sovereignty.
John 1:1-3 states, "In the beginning was the Word, and the Word was with God, and the Word was God. The same was in the beginning with God. All things were made by him; and without him was not any thing made that was made."
Notice especially verse 3: "All things were made by him; and without him was not any thing made that was made." This directly connects with the truth presented in Colossians 1:15.
The emphasis, then, of "firstborn" is one of rank and is not related to birth as we commonly think of it.
Psalm 89:27 uses the word "firstborn" in referring to David's son, but it looks ahead to Christ: "I will make him my firstborn, higher than the kings of the earth."
Since Colossians 1:17 indicates that the Lord Jesus Christ existed before all created things, He Himself is uncreated, thus eternal. This verse says, "He is before all things, and by him all things consist." He is the eternal God; therefore, He is the Supreme Being.
"Jesus Christ the same yesterday, and to day and for ever" (Heb. 13:8).