The Trinity is one God in three Persons. The Bible teaches three coexistent, co-eternal Persons who comprise the one God. Jesus is referred to as the second Person in the Trinity, because in the “Trinitarian formula” used in the Great Commission in Matthew 28:16, Jesus, the Son, is mentioned second: “Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit.”
Using the terms first, second, and third in relation to the Persons of the Trinity does not mean there are different levels of importance among those Persons. The Athanasian Creed, an early summary of Christian doctrine on the subjects of the Trinity and the deity and humanity of Christ, states that “we worship one God in Trinity, and Trinity in Unity”; also, we are careful to distinguish the three Persons while not dividing their nature and substance. As the creed says, “There is one Person of the Father, another of the Son, and another of the Holy Spirit. But the godhead of the Father, of the Son, and of the Holy Spirit, is all one, the glory equal, the majesty co-eternal. . . . In the Trinity none is before or after another; none is greater or less than another, but all three Persons are co-eternal together and co-equal.”
The Son is not inferior to the Father, but the Son did submit to the Father’s will. Jesus is called the second Person of the Trinity because He was the one who, although coexistent and co-eternal with the Father, voluntarily submitted Himself to take on human nature. In His meek and humble human existence, the Son lived in total obedience to God the Father. Philippians 2:6–8 puts it this way: “[Christ Jesus], being in very nature God, did not consider equality with God something to be used to his own advantage; rather, he made himself nothing by taking the very nature of a servant, being made in human likeness. And being found in appearance as a man, he humbled himself by becoming obedient to death—even death on a cross!” The Son is “second” in priority in the “economic Trinity”—that is, the Trinity as God has revealed Himself to us and interacts with us as human beings.
Through His obedience as the Son, Jesus purchased our salvation and has now been exalted to the right hand of the Father (Hebrews 1:3).