Dov Lew asked:
Shabbos 51b-
Why is it that if an animal goes out with an unneeded garment, it is a transgression of Shvisas Behaimah but there is never any prohibition from the Torah for a person to go out with excessive garments? Why isn't there an identical definition of a 'Masui' for both of them?
The Kollel replies:
You are bothered by the concept of "Shemirah Yeseirah" with which it is forbidden for an animal to go out. Indeed, the same underlying concept applies to man as well -- it is forbidden for a person to go out with excessive clothing. Excessive clothing is defined as something which is not normally worn in that manner during the week (such as wearing a folded garment atop one's soldier, as the Gemara explains on 58a and as Rashi explains there).