that it is the nature of knots to tighten even more in water, creating an interposition that bars the water from entering all the way, but in the case of the first clause of the mishna, which deals with one vessel inside another and where water by nature causes the top vessel to lighten and float away from the lower vessel rather than weigh down on it, I would have said that it is not considered an interposition. It is therefore necessary for the halakha to be stated in both cases.

The Gemara comments: Rabbi Ila here conforms to his standard line of reasoning in considering these two issues as one, as Rabbi Ila said that Rabbi Ḥanina bar Pappa said: They taught ten stringencies of sacrificial food here in this mishna, rather than the apparent eleven. The first five stringencies apply both to the sacrificial foods themselves and to non-sacred food that was prepared according to the standards of purity of sacrificial food, whereas the last five apply only to actual sacrificial food but not to non-sacred food that was prepared according to the standards of purity of sacrificial food. The fact that Rabbi Ila counts only ten cases in the mishna shows that he considered the two cases discussed above to be of the same category, and therefore they are counted together as one stringency.

The Gemara explains Rabbi Ila’s statement. What is the reason for this distinction? With regard to the first five stringencies, which have a connection to impurity as defined by Torah law because ignoring them can lead to a case of impurity by Torah law as opposed to merely rabbinic law, the Sages decreed these stringencies both for actual sacrificial food and for non-sacred food prepared according to the standards of purity of sacrificial food. However, with regard to the last five, which do not have a connection to impurity by Torah law, as their entire impurity is based on a rabbinic decree, the Sages decreed these stringencies only for actual sacrificial food. But with regard to non-sacred food made according to the standards of purity of sacrificial food, the Sages did not decree these stringencies for such foods.

Rava disagreed with Rabbi Ila. He said that since the reason for the stringency in the latter clause is due to concern for interposition, this implies that the reason for the stringency in the first clause is not due to interposition, but to a different reason. And with regard to the stringency in the first clause that one may not immerse one vessel within another, this is the reasoning: It is a rabbinic decree to ensure that one not immerse small vessels, such as needles and hooks, inside a vessel whose mouth is less than the width of the tube of a wineskin. In such a case the water in the bottle would not be considered attached to the rest of the ritual bath, as we learned in a mishna (Mikvaot 6:7): The joining of different bodies of water in cases of ritual baths takes place if the opening between the two bodies is at least as wide as the width of the tube of a wineskin, counting both the thickness of the wall of the tube