“I also established my covenant with them to give them the land of Canaan, where they lived as aliens. Moreover, I have heard the groaning of the Israelites, whom the Egyptians are enslaving, and I have remembered my covenant”. 

Ex 6:4, 5 NIV 

Sometimes history has some awfully long and seemingly empty periods. At other times many things happen one on top of the other and it seems to be a major turning point. 
The four hundred-year-long period the Israelites spent in Egypt was a sojourn which passed with no particularly significant events. Just work, labour, and suffering. Why God didn’t do anything in all that time we do not know. It is “empty” as far as the Bible record goes. For the people it was a soul-destroying bind. But centuries earlier God had set his covenant with Abraham, Isaac and Jacob, and the covenant involved a promise that he would establish them in the land of Canaan. It is possible that the people forgot the promise down through those centuries – or almost. Somebody must have remembered or there would be no written record – these have been penned down after they had returned to Canaan. But from God’s side the promise stood and here we find God reminding Moses about the ancient covenant. For the people it had been pain, pain and more pain. For God it was just promise. He was the God of the promise. 
He still is. And his promise today is that the salvation Christian believers know in Christ is available for all people. It is available to people in the east, in the frozen forests of Russia, the deserts of Africa, the crowded cities of Europe and America. Wherever there is pain there is the promise of God. 

Lord, it is good to know that your promise still stands.