During periods of abstinence, he wore a plain robe made of coarse linen. During periods of abstinence, he changed his diet and did not sit in his usual place when at home.
This passage is possibly part of the previous chapter, but I’ll leave arguments about that for others.
A gentleman would “purify” himself in preparation for major ritual ceremonies on the lunar calendar by changing his normal routine, eating simple food, bathing, and wearing plain clothes.
All very good for the soul.