and tell them: This is what the Lord Yahweh says: In the day when I chose Israel and lifted up my hand and swore
to the seed of the house of Jacob and made myself known to them in the land of Egypt, when I lifted up my hand to them, saying, I am Yahweh your God,
“In the day when I chose Israel.” God now reminds the people how He had chosen Israel to be His people and brought them out of Egypt.
“lifted up my hand.” One way a person swore a solemn oath was to raise his hand and swear. See commentary on Genesis 14:22.