What was the first thing God promised Abraham about the nation's duration?
God first told Abraham that there would be 430 years of sojourning, and then the nation would be brought back to Himself. That period ran from Abraham's departure out of Syria into Canaan until Moses led the people out, exactly 430 years.
Les explains that the first thing God told Abraham about the nation's duration was that 430 years would be spent sojourning, after which the nation would be brought back to Himself. Les points out that this was exactly fulfilled: 430 years from the time Abraham came out of Syria down into Canaan until Moses led them out. He then contrasts this with a later prophecy of 490 years from a particular time after the Babylonian captivity, when Nebuchadnezzar came in 606 B.C. and took Daniel and all the Jews captive back to Babylon. That 70-year captivity brings the timeline to about 526 B.C., when Ezra went back by the decree of Cyrus to rebuild the temple. Jeremiah had prophesied that the nation of Israel would go into captivity for 70 years.