Of all the words of the Passion, for me the most poignant are the words "Deus meus, Deus meus, ut quid dereliquisti me?", St Matthew gives us the actual words, "Eli, Eli lama sabacthani?", presumable to emphasise their importance in the passion narrative.
I have heard some pretty eminent scholars suggest that they are a great cry of despair by Jesus. others suggest they are a final act of hope and point to their origin in the Ps 21/22, which is a movement from misery to consolation and eventual triumph.
For me they give a profound insight into the relationship of the Jesus with his Father.
First, Jesus is praying to the Father, and yet he feels forsaken or abandoned. The whole point of crucifixion was to degrade, to dehumanise, to cut the victim off, Jesus experiences this even in his relationship with his Father. Throughout the Gospel, his relationship with God seems to be one of knowledge rather than faith, he feels, he experiences absolute intimacy with his Father. On the Cross, here, as he dies, the experience, the feelings are numb, only faith exists. It is the faith that most of us know, where we are not "strangely moved", or feel we can call on good with absolute certainty, the type faith depends on past experiences , on intuition, "when taste and touch deceiving" and we rely on "trusty hearing". In a way this pure faith, pure trust, stripped of everything, this is the type of faith most of us experience most of the time. These words identify Jesus preeminently as the man of faith.
If this is so, then perhaps here is an insight into so much else about Jesus, his understanding of himself as God, for example, or his own resurrection, these spring from his faith. In this, because "he is a man like us in all things but sin", "truly God and truly, without co-mixture", he shares with us the way all human beings relate to God, through faith. I do not think it is blasphemous to say that Jesus knew he was the "Son by nature" in the same way that I know I am a "son by adoption". Similarly he knows about his resurrection in the same way we know we will rise again, it is by faith. For human beings, Jesus included, faith is the only cord that unites us to God.