Romans 12:6

"Having then gifts differing according to the grace of God that is given unto us, whether prophecy, let us prophesy according to the proportion of faith." Since then he had sufficiently comforted them, he wishes also to make them vie with each other, and labor more in earnest, by showing that it is themselves that give the grounds for their receiving more or less. For he says indeed that it is given by God (as when he says, "according as God hath dealt to every man the measure of faith;" and again, "according to the grace given unto us") that he may subdue the haughty. But he says also that the beginnings lie with themselves, to rouse the listless. And this he does in the Epistle to the Corinthians also, to produce both these emotions. For when he saith, "covet earnestly the gifts," he shows that they were themselves the cause of the differences in what was given. But when he says, "Now all these things worketh one and the selfsame Spirit, dividing to every man severally as he will", he is proving that those who have received it ought not to be elated, so using every way open to him to allay their disorder. And this he does here also. And again, to rouse those who have fallen drowsy, he says, "Whether prophecy, let us prophesy according to the proportion of faith." For though it is a grace, yet it is not poured forth at random, but framing its measure according to the recipients, it letteth as much flow as it may find the vessel of faith that is brought to be capable of.