But in this case, you are insisting something quite different. While saying that Malachi and Isaiah speak of YHWH performing certain functions for His people, in this case you insist that the NT writers switched gears totally and are now speaking of an agent of God’s–not YHWH Himself. What happened here? It seems that you are totally going against a principle that you have repeatedly stressed.
It’s an astute comment, and I accept that there may well be subtle ways in which I am bending the evidence to fit my thesis. We all do that.
However, I don’t think it’s inconsistent to say that the Old Testament narratives are borrowed and adapted to fit the particular unique circumstance that lies at the heart of the New Testament, which is that God raised Jesus from the dead and gave him authority to judge and rule.
We have to take into account the fact that the Jews found it very difficult to believe that the Old Testament hopes (and fears) could be fulfilled through the death of Jesus. The application is not straightforward. Isaiah 40:1-5 does not speak directly of the redemption of Israel in the first century. It speaks of the return from exile. What Mark has done is to take that narrative and reapply it under different conditions, which includes the conviction that YHWH has delegated the right to rule to his Son, whom he raised from the dead. So yes, there has to be some sort of switching of gears to accommodate the central New Testament witness to the resurrection. But the structure of the Old Testament narratives remains the same.
(I’m sorry you had problems with the italics. No idea why.)