“How then shall they call on him in whom they have not believed? and how shall they believe in him of whom they have not heard? and how shall they hear without a preacher?”
King James Version (KJV)
Ro 10:14 How then shall they call on him in whom they have not believed? The passages quoted from the prophets show that the Gentiles also were to have the opportunity of salvation. Hence the duty of preaching to them is now shown. They could not "call upon the Lord" without faith. See Ro 10:13. But there could be no faith in the Lord unless they had heard of him, since knowledge is an element of faith. But they could not hear the gospel story until it was preached to them. Hence, preaching to the Gentiles was essential to carry out the purposes of God.