
What if a mikveh has 40 se’ah of water but it’s too shallow for a person to immerse in? Can you simply add mayim she’uvim (drawn water) to make it kosher?
This sugya in Chagigah 11a gets into the lomdus of shiur mikveh — whether 40 se’ah is a definition of mikveh volume or a requirement for practical tevillah.
The Ra’ah holds you can’t fix it with added water; the Rashba says you can. This core machlokes shapes how we understand the very essence of what makes a mikveh kosher.