Dear Robert,

That saying found in Mark, Matthew and Luke, which means that it appeared first in Mark and was then copied by Matthew and Luke, is one of many given a black rating by the Jesus Seminar, which means that they regarded that saying as impossible for Jesus to have said and for the same reasons that you mentioned.  Before the crucifixion of Jesus, the cross had no transformative meaning.  It was nothing other than a piece of equipment used in the Roman method of execution.  Yes, there were many crucifixions prior to Jesus, but it had no other purpose and was not something which anyone would have been invited to emulate.

I do not think anyone should read any verse of any gospel as if it were a literal quotation from a tape-recorded Jesus of Nazareth.  The sayings of Jesus contained in the gospels were first of all translations into Greek from the Aramaic originals and, secondly, they had been carried by an oral tradition for 40-70 years before being recorded.  The members of the Jesus Seminar after a study that took more than a decade color coded every saying of Jesus in the New Testament using four colors.  Red meant this saying is close to the words and ideas of Jesus himself.  It passes the authenticity test.  Pink meant the idea expressed in this saying may have originated with Jesus, but the form and context that we possess in this text have been corrupted.  Gray meant this saying is far more likely to have been the voice of the post-Jesus church read back into the life of the historical Jesus than it is an authentic word of Jesus.  Black meant that in this saying there is no echo of the voice of Jesus that can be heard speaking.  The text you mentioned is in the black category... In the Fourth Gospel all of the  sayings of Jesus, except for one (John 4:1), are coded black, which of course means that all of the “I am” sayings, which only John records, are deemed not to be the authentic words of the Jesus of history.

To say, however, that these are not the literal words of Jesus does not mean that they have no meaning.  While Jesus surely did not say, “I am the bread of life,” the fact that people found in him that which satisfied their deepest hunger helps us to understand why these words were attributed to him.

~John Shelby Spong