Introduction This is the final mishnah that clarifies what counts as "living waters."
Ahab's well and the pool in Banias cave are fit. The Ahab is the name of a river. The Banias is one of the rivers that feed into the Jordan. This well and pool are considered "living waters" and therefore can be used for the red cow ritual.
Water that has changed its color and the change arose from itself, remains fit. If the color of the water changes not because another river fed into it, but due to some cause that came from the river itself, its waters remain valid.
A water channel that comes from a distance is fit, as long as it is watched so that no one cuts it off. Rabbi Judah says: the presumption is that it is permitted. A water channel whose source is far removed counts as "living waters." However, according to the first opinion, he must watch it to make sure that someone doesn't cut it off to water his fields. If it is cut off from its source, it no longer counts as "living waters." Rabbi Judah says that we can always presume that the water channel is attached to its source. It need not be watched, for unless we know that it has been cut off, it remains valid.
If some clay or earth fell into a well, one must wait until it becomes clear, the words of Rabbi Ishmael. Rabbi Akiba says: he need not wait. If the water of a living well becomes temporarily murky because some clay or earth fell into it, Rabbi Ishmael says that he must wait until the normal color returns to use it for the red cow ritual. Rabbi Akiva says that this is not necessary.