Are You Seed of the Serpent?

John 1 John 3 explicitly links the children of the devil with Cain, reflecting his understanding of the cursing of the serpent and then of Cain. When David goes against Goliath, Goliath is described as wearing scaly armor, right? And David, what does he do? He crushes his head. So we have these conflicts emerging throughout the Old Testament built on Genesis 3.15 that's creating an expectation of someone yet to come who's going to do this fully and finally.