31 The promise of divine presence always indicates intervention (for blessing or cursing). Here it means that God would be working through the organs of speech to help Moses speak. See Deut 18:18; Jer 1:9.
32 The verb is וְהוֹרֵיתִיךָ (véhoretikha), the Hiphil perfect with a vav (ו) consecutive. The form carries the instructional meaning because it follows the imperative “go.” In fact, there is a sequence at work here: “go … and/that I may teach you.” It is from יָרָה (yara), the same root behind תּוֹרָה (torah, “law”). This always referred to teaching either wisdom or revelation. Here Yahweh promises to teach Moses what to say.
33 The form is the imperfect tense. While it could be taken as a future (“what you will say”), an obligatory imperfect captures the significance better (“what you must say” or “what you are to say”). Not even the content of the message will be left up to Moses.

In other versions

Now therefore go, and I will be with your mouth and teach you what you shall speak.”

Now go; I will help you speak and will teach you what to say.”

Now go! I will help you speak and I will teach you what to say.”

Now go! I will be with you as you speak, and I will instruct you in what to say.”

So then go, and I myself will be with your mouth, and I will teach you what you must speak.”

Now therefore go, and I will be with thy mouth, and teach thee what thou shalt say.

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