Sanhedrin 61a in Tosphot. I have asked on Tosphot that in his approach he is expanding the area of prohibition of bowing (Deuteronomy 17) to include the way of the idol not in a way of honor[quadrant IV]. And yet we see in the Gemara itself that it does a similar thing. It says we would know from "bowing" to absolve a way of dishonor to idols that one usually sacrifices to[quadrant III]. But we would not know to absolve service in a way of dishonor towards idols one worships in a different way of dishonor. So we need "How do they serve.?"to absolve that.
So we clearly are expanding some kind of prohibition into quadrant III.What could it be? It is not going the be "how do they serve?" because that is what we are about to use to tell us not to expand the the prohibition there.




That is to say we might think such and such a thing so we have a verse to exclude it. But I am wondering on the Gemara itself why would we think to expand it? Well the Gemara itself gives a reason. What is it with exposing oneself to Peor is liable, so also all types of service that are not honorable are liable. But how does that reasoning help to expand bowing to serve that is dishonorable that is its way that Tosphot requires in order to answer his question?



Actually I dont think this last answer is right, and rather the real reason we would have expanded the prohibition into quadrant III is just because idolatry is forbidden. i.e from the verse "least he will go and serve"