Chagigah 23B

עשאוה כטמא שרץ.

as they treated the tube with severity as though it had been rendered impure by contact with a dead creeping animal. Therefore, in not requiring the setting of the sun they made it noticeable that they were opposed to the Sadducees.

אלא מעתה, לא תטמא אדם, אלמה תניא: חותכה ומטבילה ⁠— טעון טבילה! ואלא: עשאוה כטמא מת. אי הכי תיבעי הזאת שלישי ושביעי,

The Talmud raises a difficulty. However, if that is so, that the tube is treated as if defiled by a creeping animal, it should not render a person impure, as something defiled by a creeping animal is impure to the first degree of ritual impurity, which cannot impart ritual impurity to people. Why, then, is it taught in a baraita: The one who cuts and immerses the tube for the red heifer ashes requires immersion himself, which shows that the tube does defile people? But rather, say that they treated it as something made impure by contact with a corpse, for such objects do defile people as well. The Talmud asks: If that is so, the tube should also require the sprinkling of the water of purification on the third and 7th days of its purification, like all things defiled by a corpse.

אלמה תניא: חותכה ומטבילה ⁠— טעון טבילה. טבילה אין, הזאת שלישי ושביעי לא! אלא: עשאוה כטמא מת בשביעי שלו,

Why, then, is it taught in a baraita: The one who cuts and immerses it requires immersion, which indicates that immersion for the tube, yes, this is required, but sprinkling of the third and the 7th day, no. Rather, you must say that they treated it as something made impure by contact with a corpse that is already in its 7th day, after its sprinklings, when it is still impure and imparts impurity to those who touch it, but requires only immersion and no further sprinkling.