How shall this be? The holy virgin appears to confine the power of God within as narrow limits as Zacharias had formerly done; for what is beyond the common order of nature, she concludes to be impossible. She reasons in this manner. I know not a man: how then can I believe that what you tell me will happen? We ought not to give ourselves very much trouble, [1] to acquit her of all blame. She ought immediately to have risen by faith to the boundless power of God, which is not at all lettered to natural means, but sways the whole world. Instead of this, she stops at the ordinary way of generation. Still, it must be admitted that she does not hesitate or inquire in such a manner as to lower the power of God to the level of her senses; but is only carried away by a sudden impulse of astonishment to put this question. That she readily embraced the promise may be concluded from this, that, though many things presented themselves on the opposite side, she has no doubt but on one point. She might instantly have objected, where was that throne of David? for all the rank of kingly power had been long ago set aside, and all the luster of royal descent had been extinguished. Unquestionably, if she had formed her opinion of the matter according to the judgment of the flesh, she would have treated as a fable what the angel had told her. There can be no doubt that she was fully convinced of the restoration of the church, and easily gave way to what the flesh would have pronounced to be incredible. And then it is probable that the attention of the public was everywhere directed at that time to the prediction of Isaiah, in which God promises that he would raise up a rod out of the despised stem of Jesse, (Isaiah 11:1.) That persuasion of the kindness of God, which had been formed in the mind of the virgin, led her to admit, in the fullest manner, that she had received a message as to raising up anew the throne of David. If it be objected that there was also another prediction, a virgin shall conceive and bear a son, (Isaiah 7:14,) I reply, that this mystery was then very imperfectly understood. True, the Fathers expected the birth of a King, under whose reign the people of God would be happy and prosperous; but the manner of its accomplishment lay concealed, as if it had been hidden by a veil. There is no wonder, therefore, if the holy virgin puts a question on a subject hitherto unknown to her. The conjecture which some have drawn from these words, that she had formed a vow of perpetual virginity, is unfounded and altogether absurd. She would, in that case, have committed treachery by allowing herself to be united to a husband, and would have poured contempt on the holy covenant of marriage; which could not have been done without mockery of God. Although the Papists have exercised barbarous tyranny on this subject, yet they have never proceeded so far as to allow the wife to form a vow of continence at her own pleasure. Besides, it is an idle and unfounded supposition that a monastic life existed among the Jews. We must reply, however, to another objection, that the virgin refers to the future, and so declares that she will have no intercourse with a man. The probable and simple explanation is, that the greatness or rather majesty of the subject made so powerful an impression on the virgin, that all her senses were bound and locked up in astonishment. When she is informed that the Son of God will be born, she imagines something unusual, and for that reason leaves conjugal intercourse out of view. Hence she breaks out in amazement, How shall this be? And so God graciously forgives her, and replies kindly and gently by the angel, because, in a devout and serious manner, and with admiration of a divine work, she had inquired how that would be, which, she was convinced, went beyond the common and ordinary course of nature. In a word, this question was not so contrary to faith, because it arose rather from admiration than from distrust.

Footnotes

1 - "Nec vero magnopere laborandum est." This is bold language, and must have sounded harsh and irreverent to a Popish ear: but in his French version Calvin uses still less ceremony. "We must not tease ourselves much to find out a way of vindicating her entirely" -- "Or il ne nous faut pas beaucoup tormenter a trouver facon de la justifier entierement." -- Ed.

Seeing I know not a man - Or, husband. As she was only contracted to Joseph, and not as yet married, she knew that this conception could not have yet taken place; and she modestly inquires by what means the promise of the angel is to be fulfilled in order to regulate her conduct accordingly.

Then said Mary unto the angel, (e) How shall this be, seeing (f) I know not a man?
(e) The greatness of the matter causes the virgin to ask this question, not that she distrusted by any means at all, for she asks only of the manner of the conceiving, so that it is plain she believed all the rest.
(f) So speak the Hebrews, signifying by this modest kind of speech the company of man and wife together, and this is the meaning of it: how will this be, for as I will be Christ's mother I am very sure I will not know any man: for the godly virgin had learned by the prophets that the Messiah would be born of a virgin.

Then said Mary to the angel, how shall this be,.... This she said not as doubting the truth of what was said; for she required no sign, as Zacharias did; nor is she charged with, and blamed for unbelief, as he was; yea, it is expressly said, Luke 1:45 that she believed: nor was this a curious question, as whether she should have this son by a man in a married state, or in her present virgin state; for she clearly understood the angel to mean the latter; and therefore her words express her admiration at it, and also her desire to be informed of the manner how it should be: as to the matter of fact, she did not dispute it, but wanted to be resolved by what means it would be brought about: she knew, by prophecy, that the Messiah was to be born of a virgin, and she perceived, by the angel's declaration, that she was that virgin, but could not imagine in what way this amazing thing should be effected; and therefore proposes this question for the following reason,
seeing I know not a man? "A husband", as the Arabic version renders it; not Joseph, nor any other man; for though she was espoused to Joseph, yet he had not taken her to wife; nor were they, as yet; come together; and before they did, she was found with child of the Holy Ghost, Matthew 1:18 she was a pure virgin, untouched by man. The words are an "euphemism", or a modest way of expressing carnal copulation; see Genesis 4:1.

How, &c.--not the unbelief of Zacharias, "Whereby shall I know this?" but, taking the fact for granted, "How is it to be, so contrary to the unbroken law of human birth?" Instead of reproof, therefore, her question is answered in mysterious detail.