Faith in the gospel of Christ comes from hearing it proclaimed.
Paul wonders why the Jewish people have not accepted the gospel. He asks whether they have not heard the gospel being proclaimed. Within that context he speaks of the importance of the preacher of the gospel, sent by God to proclaim it. Faith, he says, “comes from what is heard, and what is heard comes through the word of Christ.” The phrase word of Christ most likely means proclamation about Christ, not the words from Christ himself. This verse is related to what Paul says in Romans 1:16. The gospel about Christ, as it is proclaimed, sets people free from bondage to sin and its consequences.