Mat 23:30 And say, If we had been in the days of our fathers, we would not have been partakers with them in the blood of the prophets.
Mat 23:31 Wherefore you are witnesses against yourselves, that you are the children of those who killed the prophets.

Alternative: And you say that that if you had lived in the days of your fathers, you would not have been their partners in [shedding] the blood of the prophets. Therefore you testify yourselves that you are the children of those who killed the prophets.

Here, the relevant symbol is "blood." As the symbol of life, it is contrasted with "bones" in the previous verses as the symbol of death.

Christ first uses the term "flesh and blood" to refer to the world of the living but specifically as part of our relationships. In the "liquid" cycle of transformation, water is turned into wine (a product of intelligence) and wine is turned into blood (a product of our relationships), and blood is turned into community. He only uses the term (haima) a few times: once to describe the limits of living relationships as the source of knowledge, several times, as here, referring to the shedding of the prophets' blood, and finally, the tranformation of wine into his blood, an act that was to be passed down to his faithful.

Christ's symbolic use of blood is always caught up in relationship. We cannot overlook the part that the shedding of blood has historically paid in religious sacrifice. At the Last Supper in Mat 26:28, Christ said that the shedding of his blood was the basis of the new testament which created a new relationship between man and God. For Christ, human death is tragic because it is a temporary end of living relationships: "blessed are those who mourn." He knew that the loss of body and mind was temporary but that all relationships are completely changed by death. There are no husbands and wives in the afterlife. Our relationship with God trumps all else. Only on earth are human relationships so dear, so important. Christ lost these relationships with his death as surely as we do, which is why he wept at Gethsemane.

Here, the message of blood is twofold. The authority of the Jewish religious leaders depended on their claim of a relationship with the prophets, but their blood relationship was with their forefathers, whose real relationship with the prophets was shedding their blood. This statement becomes completely prophetic later in Mat 27:25 when these same leaders said that the blood of Christ was on both them and their children. This blood knot is complicated. The Jews are both Christ relatives and the decendants of those who were his killers. What is interesting is that, unlike their forefathers, who honored their prophets after their parents killed them, the Jews after Christ chose to deny him rather than claim him (as, for example, the Muslims do). Something had clearly changed in their relationships.

Also extended in this metaphor is blood and bone is the idea of the inside (esothen: within) and the outside (exothen: outward) discussed in the earlier verse. The blood of living relationships and the bone of bodily death are both inside of us. Christ defines what is inside as the animating spirit. The outside is just appearances. Our bones symbolize the fact that our bodies must die, but our blood symbolizes the fact that our relationships live on: if only in our childen. For those who share in the living water, the blood of Christ, death is still real a part of us but temporary. In those who shed the blood of the prophets, death is triumphant.

"Partakers" is from koinônos, which means "a partner," "a comrade," "a companion," and "a sharer of anything." It is from the Greek word meaning "common."

"Witness" is from martureô, which means "to give testimony" and "to bear witness." It as the sense of being true testimony, the opposite of the Gospels word for "false witness," pseudomartureô, which is sometimes translated as "lies."