Exodus 16:4-12

4 Then the Lord said to Moses, “Behold, I am about to rain bread from heaven for you, and the people shall go out and gather a day's portion every day, that I may test them, whether they will walk in my law or not. 5 On the sixth day, when they prepare what they bring in, it will be twice as much as they gather daily.” 6 So Moses and Aaron said to all the people of Israel, “At evening you shall know that it was the Lord who brought you out of the land of Egypt, 7 and in the morning you shall see the glory of the Lord, because he has heard your grumbling against the Lord. For what are we, that you grumble against us?” 8 And Moses said, “When the Lord gives you in the evening meat to eat and in the morning bread to the full, because the Lord has heard your grumbling that you grumble against him—what are we? Your grumbling is not against us but against the Lord.”
9 Then Moses said to Aaron, “Say to the whole congregation of the people of Israel, ‘Come near before the Lord, for he has heard your grumbling.’” 10 And as soon as Aaron spoke to the whole congregation of the people of Israel, they looked toward the wilderness, and behold, the glory of the Lord appeared in the cloud. 11 And the Lord said to Moses, 12 “I have heard the grumbling of the people of Israel. Say to them, ‘At twilight you shall eat meat, and in the morning you shall be filled with bread. Then you shall know that I am the Lord your God.’”

At the burning bush, Moses asked the Lord, “Who are you?”

The Lord’s answer: “I am who I am.” In other words, you’ll know who I am because of the way I will be. You’ll know me from what I do.

One of the themes of Exodus is the Lord’s revealing of who He is, both to the Israelites and to the Egyptians.

Look what the Lord says:

“At twilight you shall eat meat, and in the morning you shall be filled with bread. Then you shall know that I am the Lord your God.” [16:12]

The Egyptians learned about the Lord through His power to liberate the slaves. The Israelites learn about the Lord through His power to provide.

P.S. “A day’s portion every day” [v. 4] is the exact same phrase in Hebrew as chapter 5:13 and 19 when Pharaoh orders the slaves’ daily quota of bricks to be the same, despite lacking straw. The contrast: Pharaoh orders a burden every day, but the Lord offers a blessing.