Shin — the 21th Hebrew letter
ש
Symbolism
Fire, teeth, transformation; the letter of Shaddai on every mezuzah and in the priestly hands; three hundred — Gideon's refined company
What the letter is built from
Traditionally three vavs rising from one base — three flames on one lamp; a four-branched shin exists only on the head-tefillin
Its first root in Scripture
The first shin root stands in the Torah's first verse: shamayim, the heavens
Messianic thread
The shin of Shaddai guards Israel's doorposts as the lamb's blood once did. Shalom, Shabbat, Shema — the great sh-words of covenant rest on this flame-letter; the valley of Jerusalem's three ridges is said to trace a shin: the Name written into the city of the great King.
In the mystical tradition
Shin is esh, fire — the black fire of the letters on the white fire of the parchment. The three heads are the patriarchs; the hidden four-branched shin awaits the world to come.
Wisdom of the letter
Sheker (falsehood) stands on one leg's letters while emet (truth) stands square — but shin serves in both words: fire warms or burns by how it is used.