What happens when a sheep that has never given birth delivers twin males at the exact same moment? Rabbi Yossi HaGlili tackled this unusual scenario head-on, and his ruling surprised even his colleagues.
The Torah states plainly: "the males are the Lord's." Rabbi Yossi HaGlili read this as an absolute statement. If both heads emerge simultaneously and neither can be identified as the true firstborn, then both males must be given to the Kohen (a priest). The plural language — "the males" — supports this reading. When you cannot distinguish which came first, both carry the sanctity of the firstborn.
The Sages, however, disagreed. They argued that the simultaneous emergence of two lambs is physically impossible. In reality, one always comes out before the other, even if by the slightest margin. Therefore, only one of the two is the actual firstborn. Since we cannot determine which one, the owner keeps one and gives the other to the Kohen.
This debate recorded in the Mekhilta is not merely about livestock. It reveals two fundamentally different approaches to legal uncertainty. Rabbi Yossi HaGlili resolved doubt by expanding the obligation — when in doubt, give both. The Sages resolved doubt by splitting the difference — when you cannot know, divide the claim. Both methods became foundational tools in rabbinic legal reasoning for centuries to come.