I am the Lord… I will deliver you… I will redeem you… I will take you to be my people, and I will be your God, and you shall know that I am the Lord your God, who has brought you out from under the burdens of the Egyptians. I will bring you into the land I swore to give Abraham, to Isaac, and to Jacob. I will give it to you for a possession. I am the Lord (Exodus 6:6-8).
At this point in the story, God's people were trapped in Egypt and completely miserable, crying out for help. The rescue was in motion, but hadn't happened yet; the people were still languishing under a horrific ruler. They had endured genocide and slavery. But God had heard them, had mobilized a leader, had publicly promised to bring them out and--this is the part that gets me--was already talking about the rescue in past tense.
This speech has "I am the Lord" for bookends. We have the opportunity to be confident in his promises, because of who he is. What he does will always, always be consistent with who he is.
This is the Lord. I testify to his goodness.