First, before we enter into the matter itself, we must keep in mind that distinction which we previously laid down so that we do not (as commonly happens) unwisely mingle these two, which have a completely different nature. For certain men, when they hear that the gospel promises a freedom that acknowledges no king and no magistrate among men, but looks to Christ alone, think that they cannot benefit by their freedom so long as they see any power set up over them. They therefore think that nothing will be safe unless the whole world is reshaped to a new form, where there are neither courts, nor laws, nor magistrates, nor anything which in their opinion restricts their freedom. But whoever knows how to distinguish between body and soul, between this present fleeting life and that future eternal life, will without difficulty know that Christ’s spiritual Kingdom and the civil jurisdiction are things completely distinct. Since, then, it is a Jewish vanity to seek and enclose Christ’s Kingdom within the elements of this world, let us rather ponder that what Scripture clearly teaches is a spiritual fruit, which we gather from Christ’s grace; and let us remember to keep within its own limits all that freedom which is promised and offered to us in him. For why is it that the same apostle who bids us stand and not submit to the “yoke of bondage” [Gal. 5:1] elsewhere forbids slaves to be anxious about their state [1 Cor. 7:21], unless it be that spiritual freedom can perfectly well exist along with civil bondage? These statements of his must also be taken in the same sense: In the Kingdom of God “there is neither Jew nor Greek, neither male nor female, neither slave nor free” [Gal. 3:28, Vg.; order changed]. And again, “there is not Jew nor Greek, uncircumcised and circumcised, barbarian, Scythian, slave, freeman; but Christ is all in all” [Col. 3:11 p.]. By these statements he means that it makes no difference what your condition among men may be or under what nation’s laws you live, since the Kingdom of Christ does not at all consist in these things.
—Calvin, Institutes (1559), 4.20.1 (Battles edition)