But to them that are called (autois de tois klētois). Dative case, to the called themselves.
Christ (Christon). Accusative case repeated, object of kērussomen, both the power of God (theou dunamin) and the wisdom of God (theou sophian). No article, but made definite by the genitive. Christ crucified is God’s answer to both Jew and Greek and the answer is understood by those with open minds.