The Mekhilta, the great halakhic midrash on the Book of Exodus compiled in the 2nd century CE, raises a deceptively simple question about the Passover blood ritual. The Torah commands the Israelites to take "from the blood which is in the saf" and touch it to the lintel and two doorposts. But the verse seems redundant. We already know they are using blood. Why repeat it?
The rabbis detect a hidden instruction buried in the repetition. From the earlier verse (Exodus 12:7), "And they shall take from the blood," one might assume that a single dipping into the basin of blood would suffice for all three touchings — one dip of the hyssop branch, then smear it on the lintel, the left doorpost, and the right doorpost.
The Mekhilta says no. The Torah deliberately restates "from the blood which is in the saf" to teach that each touching requires its own separate dipping. Three points of contact on the doorframe, three separate immersions of the hyssop into the blood. The repetition is not careless. It is precise legal instruction disguised as narrative.
This principle — that no word in the Torah is wasted — sits at the heart of rabbinic interpretation. Every phrase carries legal weight. Even what appears to be mere literary repetition turns out to be a binding commandment about how to perform the ritual that saved Israel on the night God struck down the firstborn of Egypt (Exodus 12:12).