וַיֹּ֖אמֶר אַל־תִּקְרַ֣ב הֲלֹ֑ם שַׁל־נְעָלֶ֙יךָ֙ מֵעַ֣ל רַגְלֶ֔יךָ כִּ֣י הַמָּק֗וֹם אֲשֶׁ֤ר אַתָּה֙ עוֹמֵ֣ד עָלָ֔יו אַדְמַת־קֹ֖דֶשׁ הֽוּא׃
[Gott] sprach: Nähere dich nicht! Ziehe deine Schuhe von den Füßen, denn der Ort, auf dem du stehest, ist heiliger Boden.
Rashi on Exodus
של means DRAW OFF and take off. It is of the same root as, (Numbers 19:5) “and the iron-head slippeth off (נשל) from the handle”; (Deuteronomy 28:40) “for thine olives shall drop off (ישל)”.
Ramban on Exodus
APPROACH NOT HITHER. Moses had not yet reached the highest degree of prophecy, for at Mount Sinai he drew near unto the thick darkness where G-d was.148Further, 20:18. This also accounts for the hiding of his face [in this instance], for he had not yet reached that high [degree of prophecy of] which it was said of Moses, and the similitude of the Eternal doth he behold.149Numbers 12:8.
Rashbam on Exodus
של!, throw off!. The word is from the root נשל, meaning a form of removal, as in Deuteronomy 7,1 ונשל גוים רבים, “He dislodges many nations, etc.”