Why say to the children of Israel, I am the LORD, and I will bring you out from under the burdens of the Egyptians…
The significance of this figure, "a stretched-out arm," must have been well understood by the Israelites. The deities of the Egyptians were represented with outstretched arms, as symbols of irresistible might. In the hieroglyphics which may yet be seen upon the obelisk at Heliopolis, and with which the Children of Israel must have been familiar, two outstretched arms occur as part of the title of one of the kings, Osirtasen Racheperka, with this meaning, "Osirtasen, the sun, is might!" God's outstretched arm, therefore, is opposed to the king's; and He adds, "I will take you to Me for a people, and I will be to you a God; and ye shall know that I am the Lord your God, which bringeth you out from under the burden of the Egyptians." Moses must also have bethought him of the promise made to him upon the mountains: "See, I have made thee a god to Pharaoh": his outstretched arm was now endued with "might"; it was the instrument by which many of the plagues were brought upon the land, and by which at last Pharaoh and his host were overwhelmed.
(T. S. Millington.)
Parallel VersesKJV: Wherefore say unto the children of Israel, I am the LORD, and I will bring you out from under the burdens of the Egyptians, and I will rid you out of their bondage, and I will redeem you with a stretched out arm, and with great judgments:
WEB: Therefore tell the children of Israel, 'I am Yahweh, and I will bring you out from under the burdens of the Egyptians, and I will rid you out of their bondage, and I will redeem you with an outstretched arm, and with great judgments: