Jamieson, Fausset and Brown on Romans 10:14-15

14-15. How then shall they call on him in whom they have not believed? and ... believe in him of whom they have not heard? and ... hear without a preacher? and ... preach except ... sent?--that is, "True, the same Lord over all is rich unto all alike that call upon Him. But this calling implies believing, and believing hearing, and hearing preaching, and preaching a mission to preach: Why, then, take ye it so ill, O children of Abraham, that in obedience to our heavenly mission (Ac 26:16-18) we preach among the Gentiles the unsearchable riches of Christ?"