John Calvin in Institutes of the Christian Religion:
If God has willed this treasure of understanding to be hidden from his children, it is no wonder or absurdity that the multitude of men are so ignorant and stupid! Among the “multitude” I include even certain distinguished folk, until they become engrafted into the body of the church. Besides, Isaiah, warning that the prophetic teaching would be beyond belief, not only to foreigners but also to the Jews who wanted to be reckoned as members of the Lord’s household, at the same time adds the reason: “The arm of God will not be revealed” to all [Isa. 53:1 p.]. Whenever, then, the fewness of believers disturbs us, let the converse come to mind, that only those to whom it is given can comprehend the mysteries of God [cf. Matt. 13:11].