Mary said to the angel, "How can this be, seeing I am a virgin?"
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. 