Mikvah

1) (Vayikra 11:36) ("But a spring or a pit where waters are gathered shall be clean; and he who touches their carcass [the carcass of the animals mentioned above] shall be tamei.") If it were written (only) "a gathering of waters shall be clean," I would think that even if he filled up (containers of water and carried them) on his shoulder and made a mikvah ab initio that it would be valid; it is, therefore, written "a spring" — Just as a spring is made by Heaven, so a mikveh must be made by Heaven. — But if so, I would say: Just as there is no involvement of man in a spring, so there must be no involvement of man in a mikveh — to exclude one's placing his vessels on the roof to dry, their filling up with (rain) water, (their breaking, and filling up a pit, in which instance I would think that the water is considered "drawn" and that the pit is pasul as a mikvah) — it is, therefore, (to negate this,) written "a pit." If so, I would think that a pit in a boat (i.e., a cavity into which sea water is admitted) would be valid; it is, therefore, written "a spring." Just as a spring is ground-based, a pit, too, must be ground-based. If so, I might think that just as a spring cleanses with any amount (that covers the object), so a mikvah cleanses with any amount. It is, therefore, written "But a spring" — a spring cleanses with any amount, but a mikvah requires forty sa'ah.

Mikvaot may be made clean [by joining drawn water from] a higher [mikveh to valid water] from a lower [mikveh or drawn water from] a distant [mikveh to valid water] in a [mikveh] near at hand. How so? One brings a pipe of earthenware or of lead and puts his hand beneath it till it is filled with water; then he draws it along till [the two waters] touch even if it be by a hair's breadth it is sufficient. If in the higher [mikveh] there were forty seahs and nothing in the lower, one may draw water and carry it on the shoulder and place it in the higher [mikveh] till forty seahs have flowed down into the lower [mikveh].

Three mikvehs, two of which held twenty seahs [of valid water] and the third held twenty seahs of drawn water, and that holding drawn water was at the side: If three persons went down and immersed themselves in them and [the water of the three mikvehs] joined, the mikvehs are clean and they that immersed themselves become clean. If the one holding the drawn water was in the middle and three persons went down and immersed themselves in them and [the water of the three mikvehs] joined, the mikvehs continue as they were before and they that immersed themselves are as they were before.

Mikvaot can be joined together [if their connection is as big] as the tube of a water-skin in thickness and in space, in which two fingers can be fully turned round. If there is a doubt [whether it is as big] as the tube of a water skin or not, it is invalid, because [this is a mitzvah] from the Torah. The same applies also to the olive's bulk of a corpse and the olive's bulk of carrion and the lentil's bulk of a sheretz. Anything which remains in [the space measuring] the tube of a water-skin lessens [its measure]. Rabban Shimon ben Gamaliel says: if it is any water creature whatsoever, [the mikvaot] remain clean.

These invalidate the mikveh and do not raise it up to [the required quantity]: Drawn water, whether clean or unclean, water that has been used for pickling or for boiling, and grape-skin wine before it becomes vinegar. How do they make the mikveh invalid and do not raise it up [the required quantity]? If a mikveh contained forty seahs less a kortov, and a kortov of these fell into it, it does not raise it up [the required quantity]; And if there were three logs of any of these, they would invalidate the mikveh. But other liquids, and the juice of fruits, brine, and liquid in which fish has been pickled, and grape-skin wine that has fermented sometimes raise it up to [the required quantity] and sometimes do not raise it up. How so? If a mikveh contained forty seahs less one, and a seah of any of these fell in it, it does not raise it up to [the required quantity]. But if the mikveh contained forty seahs and a se'ah of any of these was put in and one seah was removed, the mikveh is still valid.

Water from pickling, vegetable broths, and not-yet-fermented grape pomace and, similarly, dyed waters invalidate the mikveh when at (a volume of) 3 lugin. But any other liquids, fruit juices, fish pickling liquid, and fermented grape pomace do not invalidate the mikveh which is missing 3 lugin, and they also do not complete it to make it valid. So if it had 39 se'in and one se'ah of these (liquids) fell in, they do not complete it. But if it had 40 se'ah and one se'ah of these (liquids) fell in, and one took out one other se'ah, this is valid even if one did this 19 times. But with drawn waters, if one se'ah fell into 40 se'ah of valid waters, and one took out one other se'ah, and one se'ah of valid water fell in, even if one did this forever, it would be valid.