How many lambs were needed for the first Passover? The Mekhilta tackles this question with characteristic precision. One might initially think that a single lamb would suffice for an entire extended family. But the Torah specifies in (Exodus 12:3): "a lamb for a household."
The word "household" here means a family unit, as confirmed by (Numbers 1:2), which uses "household" to mean a clan or family group. So the requirement is one lamb per family, not one lamb for everyone.
But the rabbis pushed further. What if ten separate families lived together in a single house? Would one lamb cover them all? After all, they share a physical dwelling. The answer is no — because the Torah also says "a lamb for a house," using the word "house" in addition to "household." This seemingly redundant phrasing creates two distinct requirements. "Household" establishes the family unit. "House" establishes the physical dwelling. Together they mean: one lamb per family group occupying one house.
This passage illustrates one of the Mekhilta's most important interpretive techniques — using apparent redundancies in the Torah to generate new legal distinctions. When Scripture could have said something once but chose to say it twice in slightly different ways, the rabbis treated each variation as carrying independent legal significance. A single extra word — "house" alongside "household" — was enough to determine how the Passover sacrifice would be organized across an entire nation.