What was the first thing God did after Adam and Eve fell?
After Adam and Eve fell, God first set in motion the coming of the seed of the woman. In Genesis 3:15 He declared enmity between the serpent and the woman, between their seeds, and promised the woman's seed. Scripture identifies that seed as Christ, so the promised coming was first voiced right after the fall.
Les explains that in Genesis 3:15 the Lord is conversing with the devil and says He will put enmity between the serpent and the woman, and between the serpent's seed and her seed. The important word is "seed," specifically the seed of the woman. Les points out that Galatians tells us plainly who the seed of the woman is: Christ. Therefore, right after Adam and Eve fell, God promised that the first thing He would do was set in motion the coming of the seed of the woman. This is where His promised coming is first voiced, establishing the promise of the Redeemer immediately after the fall.
And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel.