Isaiah's prophecy reveals God's dismay over the empty, useless worship practices of God;s people. These people think they're doing just what God wanted, but they should think again. God is clearly upset as the people have designed ways and practices that suit them, not God.
Paul is explaining how Jesus, the crucified Savior, is the wisdom and strength of God. Really? How is it that the one who is supposed to be saving ends up dying, slain on a cross of the Empire? That isn't a savior; that's a dead loser, the Corinthians seem to feel. Paul explains how God's wisdom is the world's foolishness (and vice versa).
Take up the challenge in these passages by checking out the sermon video below.