Masechet (tractate) Eduyot, Perek Chet (Chapter Eight), Mishnah Daled (fourth). In this Mishnah, we’ll talk about three different testimonies that Rebbe Yosef ben Yoezer gave. The Mishnah says that Rebbe Yosef ben Yoezer, who was the rabbi of Tzeredah, testified about the Ayal grasshopper. The Ayal grasshopper had a very long head, and he testified that it is still kosher (fit to eat), even though it looks different from the other ones that are known to be permitted to be eaten.
Second testimony: He also testified about the liquids in the butchering place of the Bet HaMikdash—the blood and the water there—that they’re tahor, that they’re pure, and that they cannot become tameh (ritually impure). Liquids can usually become tameh at a deRabbanan (rabbinic) level. But Rebbe Yosef says that when we’re talking about the Bet HaMikdash, they did not impose this restriction on the Bet HaMikdash because they wanted to make sure that sacred items did not become impure.
Number three: He said that somebody who definitely touched a corpse in a public domain is tameh. The idea behind this testimony is to imply that if there’s a doubt about somebody—if we don’t know whether he touched a corpse in a public domain—he’s tahor. Only when he definitely touched a corpse in a public domain is he tameh.
After Rebbe Yosef gave these three rulings, the rabbis after this weren’t pleased with his lenient rulings, and they called him Yosef, the one who allows, because he permitted three things that had been forbidden before he came and gave his testimony.