From a first century Jewish perspective, I don’t think that this kind of teaching would have been perceived as too new or shocking.

There is a number of sections in the Old Testament that support this claim, but the most relevant I think would be the Ten Commandments. The Ten Commandments feature twice in the Jewish Bible, once in Exodus and once in Deuteronomy. The Ten Commandments would have served as a moral guideline for practicing Jews and would have already touched on the belief in treating others fairly, although the teachings of Jesus in the Bible are considerably more liberal in respect to justice.