The four passages, all of which say "bind"

The four scrolls carry four passages, and the reason these four is that these four are the ones that give the instruction:

· Exodus 13:1–10 — Kadesh li, "consecrate to me every firstborn." The Exodus, and the sign upon the hand.
· Exodus 13:11–16 — V'haya ki yeviacha, "when the Lord brings you into the land." The redemption of the firstborn, and the child who asks what this means.
· Deuteronomy 6:4–9 — the Shema. Hear, O Israel; and love; and these words on your heart, and taught to your children, and bound on your hand, and between your eyes, and on your doorposts.
· Deuteronomy 11:13–21 — V'haya im shamoa, "if you truly listen." The rain in its season, and the same binding, and the same doorposts.

Two are about coming out of Egypt and two are about listening, and all four contain the same clause. That is the entire selection principle: the object is assembled out of the verses that command the object. It is self-specifying, in the way a recipe printed on the tin is self-specifying, and there is something worth sitting with in a commandment whose content is its own instructions.

The arm-box's single scroll carries all four in order on one piece of parchment; the head-box's four each carry one. The scribal requirements are exacting and the letters must be written in order, which is why a single scroll is unrepairable in a way a Torah scroll is not.