God does not arbitrarily pick people for mercy, and people to "harden" (Rom 9:14-18). Historical context is important: personal and national issues that Paul references. The rise and fall of nations is not an accident, but a direct consequence of their openness or opposition to God's will (Exo 5:1-2). Jesus Christ controls history; there are at least four evidences from scripture: (1) After the resurrection Christ is in charged (Psa 2:1-12, Act 13:33); (2) Christ will reign from Jerusalem; the Lord is Priest and King; Jesus is the Lion of the Tribe of Judah; His military defeat of enemies is sure (Psa 110:1-7); (3) Jesus has ultimate authority (Joh 5:22, Mat 28:18); (4) We have a hope in Christ - He is rich because of us as His inheritance; the power exerted during Jesus' resurrection is the power He is now directing toward us; He has been given dominion (Eph 1:15-23). (5) History supports and gives evidence to the promise given to Abraham (Gen 12:1-3). Comfort and confidence for us: Every power is ordained by God (Rom 13:1). God is working toward his eternal purpose (Isa 46:10, Eph 9:1, Eph 9:11). All things are working for good to the faithful believer (Rom 8:28). Preview: Moses was warned by God about Pharaoh (Exo 3:19, Exo 4:21, Isa 46:10); Pharaoh hardens his own heart before God confirms it. Process: Pharaoh was considered a god (Exo 5:1-2); Moses says God brought the trouble on Israel and Egypt. Moses knows God is in control (Exo 5:3-23). Performance: God says "I will harden Pharaoh's heart" (Exo 9:34-35) but not until Pharaoh hardens his own (Exo 7:3, Exo 7:13-14, Exo 7:22, Exo 8:15-32, Exo 9:12). Hebrews chapters 3 & 4 reminds the Jews of the choices the Exodus generation made. There comes a point when God chooses for us, when Mercy and Grace is withdrawn.
After 40 years in the Egyptian palace then 40 years in the desert then 40 years leading Israel to their land Moses' life can actually teach us about living in the time we live.