"Who died on the cross? Was it God or was it man? If it was God, I cannot understand how a God can die" - Jose Rizal, Philippine national hero

For those who believe that Jesus is both God and man, the question who or what died on the cross is a very difficult one.  This is demonstrated by the conflicting answers various Trinitarian groups give.  Some Trinitarians claim that only the Second person of the Trinity died while others believe that all of God died (1).  Some believe that the second person died completely while others believe that only the human nature of Jesus died.  No wonder Karl Keating, a prominent Catholic apologist, included this question in his article "The World's Toughest Catholic Quiz".

Since Old Testament times the Bible has clearly taught that God is only one and not two, three, or more. This is what Moses affirmed when he said, "Hear, O Israel: the Lord our God, the Lord is One" (Deut. 6:4).

Some people understand the oneness of God to mean singularity in essence but plurarity in person. In other words, they believe that God is not simply one but two-in-one or three-in-one. However, the Bible never defined God in terms of Greek notions of essences and  persons.  What the Bible taught was a God who spoke not as a group of persons but as a single person as can be confirmed in thousands upon thousands of verses where singular personal pronouns such as I, me, he, him, and matching singular verbs and adjectives were used to describe God.

There are a few verses that seem to apply plural pronouns (e.g. "us") to God but a thorough study of them reveals not a multipersonal being but a condescending  God relating to His heavenly hosts. On the other hand, whenever God asserts and emphasizes His uniqueness, God would always use singular personal pronouns.