The second day in the O Antiphons:
O Adonai, et Dux domus Israel, qui Moysi in igne flammae rubi apparuisti, et ei in Sina legem dedisti: veni ad redimendum nos in brachio extento..
O Lord and Ruler the house of Israel, who appeared to Moses in the flame of the burning bush and gave him the law on Sinai: come, and redeem us with outstretched arms.
Exodus 3:2: “An angel of the Lord appeared to him in fire flaming out of a bush. As he looked on, he was surprised to see that the bush, though on fire, was not consumed”.
Exodus 6:6: “Therefore say to the Israelites: I am Yahweh. I will free you from the enforced labor of the Egyptians and will deliver you from their slavery. I will rescue you by my outstretched arm and with mighty acts of judgment”.