The verse (Exodus 13:9) states, "And it shall be to you as a sign upon your hand and as a memorial between your eyes." The Mekhilta derived from the sequence of this verse a precise halakhic ruling about the order in which tefillin (leather phylacteries worn during prayer) are donned and removed.
The logic is direct. The verse mentions the hand tefillin first and the head tefillin second: "upon your hand" comes before "between your eyes." This sequence establishes the order for putting them on — the hand tefillin first, then the head tefillin.
But there is a second inference. If the hand tefillin must already be in place when you put on the head tefillin, then the head tefillin must be removed first when you take them off. Otherwise, there would be a moment when the head tefillin are on but the hand tefillin are not — violating the verse's implied requirement that the hand precedes the head.
From this the sages derived a formal rule: when putting on tefillin, you begin with the hand and then place the head. When removing tefillin, you take off the head first and then the hand. The hand tefillin are always the first on and the last off.
This ruling, derived from the word order of a single verse, became codified in the Shulchan Arukh (Orach Chaim 28:2) and is observed by every Jew who wears tefillin today. The sequence is not arbitrary or traditional — it is read directly out of the Torah's own syntax, where even the order of phrases within a verse generates binding law.