JUSTIN MARTYR:
In order to ensure that someone does not accuse us of saying the same things as the poets, who say that Zeus came to women for sexual pleasure, we will explain the words of this prophecy clearly. The phrase “behold, the virgin shall conceive” means that the virgin would conceive without intercourse. If she had in fact had intercourse with someone, she would not have been a virgin. God’s power came on the virgin, overshadowed her and caused her to conceive while she remained a virgin.