shemot 3:5
*1. Source
יֹּ֖אמֶר אַל־תִּקְרַ֣ב הֲלֹ֑ם שַׁל־נְעָלֶ֙יךָ֙ מֵעַ֣ל רַגְלֶ֔יךָ כִּ֣י הַמָּק֗וֹם אֲשֶׁ֤ר אַתָּה֙ עוֹמֵ֣ד עָלָ֔יו אַדְמַת־קֹ֖דֶשׁ הֽוּא׃ And [God] said, “Do not come closer! Remove your sandals from your feet, for the place on which you stand is holy ground!”
2. Explanation
God says "do not come any closer." The idea is to to convey the uniqueness of the event to moses.Because the event was special, god asks him to take his shoes off. Moses is stepping on holy land. He delivers a clear message: Moses is in a very unique situation: God wants to speak to him personally and help him understand the event's importance.