Honoring the Torah scholar, the talmid chacham. In the context of defining "Derekh Eretz" - the Torah teaches us manners, etiquette, and how to be a mentsch. Changing clothes, not wearing patched shoes, oil-stained garments as matters of respect. Note the higher standard for the talmid chacham, presumably given what he represents. The significance of presentability goes beyond what we often recognize in our casual era. Also: Stains on a donkey's saddle - when is it a barrier? A comparable case is brought to answer the question - about those who have stained garments on both sides. Linguistically, the term "bana'in" needs explanation, and is linked to the Torah scholars who "build" the world. The expectation is that Torah scholars are so meticulous that even uneven stitching on a garment wouldn't be seen, and that same meticulousness is evident in his Torah knowledge as well. And distinguishing between talmidei chachamim who are leaders as compared to those who have a depth and breadth of knowledge, but don't undertake that role.