The lamp that will not stand still

Zohar III:218b–219a, the passage everyone cites for the sway. Its starting point is Proverbs 20:27 — נֵר יְיָ נִשְׁמַת אָדָם, "the soul of man is the lamp of the LORD" — read not as a compliment but as a description of behaviour. A lamp-flame is fed from below and reaches upward and never once holds still. So a soul, being a flame, does the same, and the moment a word of Torah is spoken the light is kindled and the person carrying it begins to move.

Which makes the sway involuntary by design — not a technique you adopt but a symptom you display. That is an unusual claim about a posture. Most of the postures in this room are instructions; this one is offered as a diagnosis. The flame is not told to flicker. Layer: Zoharic, late 13th century. The competing explanation in the Kuzari is a century and a half older and entirely mundane, which is worth knowing before deciding which one you find more convincing.