Jamieson, Fausset and Brown on Romans 11:32

32. For God hath concluded them all in unbelief--"hath shut them all up to unbelief"

that he might have mercy upon all--that is, those "all" of whom he had been discoursing; the Gentiles first, and after them the Jews [Fritzsche, Tholuck, Olshausen, De Wette, Philippi, Stuart, Hodge]. Certainly it is not "all mankind individually" [Meyer, Alford]; for the apostle is not here dealing with individuals, but with those great divisions of mankind, Jew and Gentile. And what he here says is that God's purpose was to shut each of these divisions of men to the experience first of an humbled, condemned state, without Christ, and then to the experience of His mercy in Christ.