He gives two reasons for why he will liberate his people:
his promise to Abraham, Isaac, and Jacob (see Genesis 15:14);
Israel’s groaning when they were enslaved in Egypt.
This is how God’s faithfulness and his compassion blend together: he hears the groaning of the slaves, and he thinks of the promise he made.
God has everything under (his) control: to Abram he has already mentioned that the Israelites would be oppressed, but that God will stand up for them, and that the fourth generation will return to the Promised Land.
4 I also established my covenant with them to give them the land of Canaan, the land in which they lived as sojourners.