שופטים ג:טו פירוש: רש״י, Metzudat David וMetzudat Zion

Whose right arm was immobile. Yonasan renders "A man whose right arm was shrunken." "Gamid" in the Aramaic always indicates something shrunken by disease, "retrait", "shrunk" in old French. He could not utilize his right arm. In Hebrew, "closed", as in "Let not the well close its mouth over me."⁴Tehilim, 69:16. His right arm was "closed"—he could not utilize it.

from the tribe of Benjamin

A matter of contraction as in Psalm 69: 16 "Don't let the mouth of the Pit not close over me." It is to say it is as if his right hand was contracted because he didn't extend it.