The concept of the Triune God is often the most difficult for Christians and non-Christians to grasp. There has been much confusion on this topic for centuries, leading to all sorts of questions. Here is one such puzzling question: If all three members of the Godhead are truly equal, why was it Jesus Christ (God the Son) who died for our sins and not God the Father or God the Holy Spirit?
God is one all powerful Entity who, before He even created the world, foresaw the fall of mankind into sin and the need to institute the plan of salvation. (See John 16:30 and Romans 11:33,34.) He chose to separate Himself into three Personalities… all unified in one Entity yet each with an individual purpose.
God the Father remains the center… the loving Father and the righteous judge, who is so pure and holy that sin cannot even existence in His presence. (See Ecclesiastes 3:17; 2 Timothy 4:8; Psalms 68:2.) God the Holy Spirit is the presence whose duty it is to enter into the hearts of men, teach them the ways of God, and guide them in the truth. Simply put: He is our conscious and as long as we are open to Him, He will be with us. (See John 14:26; 15:26; John 16:7-14; Ephesians 1:13; 4:30.)
Neither God the Father nor God the Holy Spirit would die in our place because that is not how God designed the plan of Salvation. First of all, as mentioned before, sin literally cannot exist in God the Father’s presence. If He came down to earth, all of sin would burn… we would burn and the earth would burn. In fact, that is what the Bible says will happen at Christ’s second coming when He returns with God the Father and all of the angels. (See Psalms 68:2; Malachi 4:1,3; 1 Thessalonians 4:13-18.) Also, according to Revelation 20:9, that is how sin will be eradicated once and for all. Back to the point: being sinful as we are, humans just cannot exist in God the Father’s physical presence. God the Holy Spirit would not die for us because that is not His purpose.
Which brings us to the third member of the Godhead: God the Son. He is a mixture of human and divine. Being born in human flesh shielded humanity from the holiness and purity that is God so people could actually approach Him. Christ existed before the world even began for this purpose. Throughout the old Testament, we read of sinful people being in the very presence of God… but if it was the presence of God the Father, the people would have died due to their unholiness, so we know it was actually God the Son who resided with man. God the Son was in the burning bush, God the Son was the cloud by day and the pillar of fire by night that lead the Israelites, God the Son allowed Moses to view the back of his head upon Mount Sinai, God the Son revealed Himself to Joshua, God the Son walked with Shadrach, Meshach, and Abednego in the fiery furnace, etc. etc.
God the Son’s purpose, from before the world was created, is to be the mediator between God the Father and mankind. (See 1 Timothy 2:5.) In Christ’s own words, “I am the way, the truth, and the life: no man cometh unto the Father, but by me.” (John 14:6)
For more insight on why Jesus had to die, try the article It is Finished by Rolf Pohler.