A rabbinic injunction enacted because of an incident TB Haggigah 23

Today’s daf TB Haggigah 23 is very complicated, difficult, and not relevant to our modern lives because we are not at all concerned about ritual readiness, taharah, and ritual unreadiness, tumah. When a person or an object comes in contact with a corpse, he or the object becomes ritually unready and has to go through a complicated weeklong ritual to become ritually ready again. This process is described in Numbers 19:1-22 and elaborated in massekhet Parah (by the way, massekhet Parah contains only Mishna and no Gemara) A unique feature of this process is the sprinkling of a mixture of red heifer ashes and spring water, mai hatat-מי חטאת, by the kohain upon the ritually unready person. One need not go to Jerusalem for this ritual for the mai hatat because the mai hatat could be transported all throughout the land. Because of an incident, the rabbis enacted a rabbinic rule how the mai hatat should be transported.

“As it is taught in a baraita: A person may not carry the water of purification and the ashes of purification and transport them across the Jordan River, and this is if he is on a boat. Nor may he stand on one side of the river and throw them to the other side. Nor may he float them across the river. Nor may he ford the river riding on an animal or on his friend and carrying the water or ashes of purification, unless his feet are touching the ground as he fords the river. But he may transfer them across the river over a bridge without concern about transferring them improperly. This decree applies both to the Jordan and to other rivers. Rabbi Ḥananya ben Akavya says: The Sages prohibited these acts only in the Jordan River, and only if he transports them in a boat, and in circumstances exactly like those of the incident that occurred.

“The Gemara inquires: What was the incident that occurred? Rav Yehuda said that Rav said: There was once an incident involving a person who was transferring water of purification and ashes of purification in the Jordan, and he was on a boat, and an olive-bulk from a corpse was discovered stuck in the floor of the boat, over which the water of purification had passed, thereby rendering them impure and invalid. At that time the Sages said: A person may not carry water of purification and ashes of purification and transport them across the Jordan, and this is if he is on a boat.” (Sefaria.org translation)

Because of this incident when the mai hatat itself became impure, invalid, and unusable, sages extended the prohibition of transporting the mai hatat on all boats and all bodies of water. Rabbi Ḥananya ben Akavya limited the scope of the enactment to only in a boat and in circumstances exactly like those in the boat while sailing upon the Jordan River.

Because of the sanctity of mai hatat and its importance rendering people who are ritually unready ritually ready, Rambam poskins according to the sages’ opinion. (Mishneh Torah, Sefer Tahrah, Hilkhot Parah Adumah, chapter 10 halakha 2)