John Calvin Commentary Isaiah 62:5

"For as a young man marrieth a virgin, so shall thy sons marry thee; and as the bridegroom rejoiceth over the bride, so shall thy God rejoice over thee." — Isaiah 62:5 (ASV)

For as a young man marries a virgin. This verse contains nothing more than an explanation and confirmation of the preceding verse. Now, there appears to be a sort of contradiction in this respect: in the latter clause he makes God the only Husband of the Church, while in the former clause he assigns to her many husbands.

But the solution is easy; for, when this marriage of the Church is spoken of, there is only one Husband, that is, God, who always claims that title for Himself; and that is fulfilled in Christ, to whom, as Paul says, the pastors espouse the Church as a chaste virgin (2 Corinthians 11:2). Yet this does not prevent the metaphor of marriage from being used to describe the unity of faith that all the children of God have with their mother, the Church.

Furthermore, it is consistent with God being the Husband of His Church that He marries to His Church all the nations that are gathered to her; for, when she is without children, she may be said to be widowed and solitary. This is said, therefore, even with respect to God, who, by ratifying with His guidance the sacred harmony between the members of His Church, extends the effect of marriage to the whole body.

Therefore, it ought to be inferred that the Church of God will be truly populous, that is, will have many children, when she is united to God her Husband. For we must begin with God, so that He may preside over His Church, and that under His guidance we may be gathered into her bosom; for then the marriage will be truly sacred.

Otherwise, a vast multitude of people will not constitute a church, but rather an abominable brothel; as we see that in Popery there is boasting of the name of God, and yet the majesty of God is dishonored in it by frightful sacrilege.