45 Heb “and Yahweh spoke to Moses saying.” This has been simplified in the translation as “he said to him” for stylistic reasons.
46 The verb is דַּבֵּר (dabber), the Piel imperative. It would normally be translated “speak,” but in English that verb does not sound as natural with a direct object as “tell.”
47 The clause begins with אֵת כָּל־אֲשֶׁר (’et kol-’asher) indicating that this is a noun clause functioning as the direct object of the imperative and providing the content of the commanded speech.
48 דֹּבֵר (dover) is the Qal active participle; it functions here as the predicate in the noun clause: “that I [am] telling you.” This one could be rendered, “that I am speaking to you.”

In other versions

the Lord said to Moses, “I am the Lord; tell Pharaoh king of Egypt all that I say to you.”

he said to him, “I am the Lord. Tell Pharaoh king of Egypt everything I tell you.”

he said to him, “I am the Lord; tell Pharaoh king of Egypt everything I am telling you.”

he said to him, “I am the Lord! Tell Pharaoh, the king of Egypt, everything I am telling you.”

And Yahweh spoke to Moses, saying, “I am Yahweh. Speak to Pharaoh, the king of Egypt, all that I am speaking to you.”

That the Lord spake unto Moses, saying, I am the Lord: speak thou unto Pharaoh king of Egypt all that I say unto thee.

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