Who Died on Good Friday?
The centerpiece of Good Friday is the cross of Jesus Christ. On the Friday before Easter Jesus was crucified and died. This creates a dilemma in the mind of some. If Jesus is God, how could he die? After all, God cannot change (Malachi 3:6), so how are we to make sense of Jesus’ death? Was it real?
Believe it or not, some people in church history said it wasn’t! Early on, there was a heretical group that plagued the Christian church called the Gnostics. This group was known for believing that the redemption of our spirits could be gained through the acquisition of secret knowledge.  The Gnostics also didn’t like matter very much, so the idea that Jesus had a body, and that he suffered was out of the question. 
There were also those who were so determined to safeguard the transcendence of God that they couldn’t fathom the idea of “God suffering.” One such person who maintained this position was the heretic Nestorius. Nestorius’ contention was that the Divine Person (the Word in John 1:1) couldn’t share in human suffering. This caused him to distinguish sharply between the two natures of Jesus Christ (human and divine). In fact, sometimes it even seemed like Nestorius was splitting Jesus into two persons, where the Divine person would act on some occasions, and the assumed human would act on others. 
This may be a little confusing, but it highlights the fact that this issue was a sticky one for the early church. Nevertheless, early Christian leaders like Ignatius of Antioch seemed to have had no problem talking about God “suffering.”  And in places like Acts 20:28, Paul could say that God obtained the church “with his own blood.” How then are we to make sense God suffering and dying?
The answer of the Church Fathers against the early heretics was this: The Eternal Word who cannot suffer and die (he’s eternal!) assumed humanity, was born of a Virgin, and suffered and died in the flesh which he assumed. Because he assumed humanity, the suffering and death are truly said to be God’s (it’s also for this reason that we can say things like, “God was born of a Virgin”). Thus, in the incarnation, the Eternal Word took to himself flesh that was capable of suffering so that he might die for sinful humanity. 
The Godhead doesn’t suffer. Jesus never ceased to be eternal, or impassible.  The mystery and the wonder of Christ’s cross is that the impassible God took on flesh so that he might make our suffering his own.  Insofar as that is the case, we can say that God the Word died on Good Friday. Let us bow in humble adoration of this God, impassible, yet taking our plight, eternal, yet murdered. Our salvation was not wrought by a mere man, nor was it accomplished by a phantom spirit, but by the crucified Lord of glory himself (1 Corinthians 2:8). On this Good Friday, let us not simply meditate upon the cross, but who it was that hung there for the race of mankind.
 Jaroslav Pelikan, The Emergence of the Catholic Tradition 82.
 This was also the view of the Docetic heresy. “Docetism narrowly defined is the view that the founder of Christianity had only an apparent, not a real human body and was subject to the human experience of birth, fatigue, thirst, hunger, suffering, death, and the like in appearance only, in reality being immune from them.” Paul L. Gavrilyuk The Suffering of the Impassible God, 79.
 Donald Fairbairn, Grace and Christology in the Early Church 54.
 Ignatius, Rom. 6.3; Cf. Eph 1.1.
 In the words of Pelikan, “He was incapable of suffering but took on a flesh that could suffer, so that the suffering of his flesh could be said to be his own.” Pelikan, Emergence 231.
 To be impassible means the Godhead is immune from suffering. This is why in order to suffer for us, the Word had to take on flesh. He was, “… passible in his flesh, impassible in his Godhead; circumscript in the body, uncirumscript in the Spirit; at once earthly and heavenly, tangible and intangible, comprehensible and incomprehensible; that by one and the same Person, who was perfect man and also God, the entire humanity fallen through sin might be created anew.” Gregory of Nazianzus Letters on the Apollinarian Controversy, Ep. 101.
 “And we confess that he who was begotten from God the Father as Son and God only-begotten, though being by his own nature impassible, suffered in the flesh for us, according to the Scriptures, and he was in the crucified flesh impassibly making his own the suffering of his own flesh. So by the grace of God he tasted death for everyone…” The Third Letter of Cyril to Nestorius.