Notes from Genesis 15:6
Although Abram had been demonstrating his faith through his actions, it was his belief in the Lord, not his actions, that made Abram right with God (Romans 4:1-5). We, too, can have a right relationship with God by trusting him. Our outward actions--church attendance, prayer, good deeds--will not by themselves make us right with God. A right relationship is based on faith--the heartfelt inner confidence that God is who he says he is and does what he says he will do. Right actions will follow naturally as by-products.

Notes from Exodus 9:12
God gave Pharaoh many opportunities to heed Moses' warnings. But finally God seemed to say, "All right, Pharaoh, have it your way," and Pharaoh's heart became permanently hardened. Did God intentionally harden Pharaoh's heart and overrule his free will? No, he simply confirmed that Pharaoh freely chose a life of resisting God. Similarly, after a lifetime of resisting God, you may find it impossible to turn to him. Don't wait until just the right time before turning to God. Do it now while you still have the chance. If you continually ignore God's voice, eventually you will be unable to hear it at all.