כְּשָׁמִ֛יר חָזָ֥ק מִצֹּ֖ר נָתַ֣תִּי מִצְחֶ֑ךָ לֹֽא־תִירָ֤א אוֹתָם֙ וְלֹא־תֵחַ֣ת מִפְּנֵיהֶ֔ם כִּ֛י בֵּֽית־מְרִ֖י הֵֽמָּה׃ (פ)
我使你的額頭像堅鐵，比磐石更硬。你不要怕他們，也不要在他們面前驚慌，因為他們是悖逆之家。
Rashi
As shamir It is a kind of worm, to which they show a stone, and it [the stone] splits in front of it. [Gloss: Another explanation: Shumir is a term for a strong rock, and in Targum Yerushalmi it is used as the translation of צוּר, rock, and so too is the Targum of מִצוּר הָחֲלָמִישּׂ as מִשְּׂמִיר טִנָרָא “out of the flinty rock” (Deut. 8:15). Shamir also means the strongest iron. For just as the strongest rock is called shamir, so is the [element] iron called shamir because of its strength. [This does not appear in all editions.]