Therefore. To show that your perversity cannot change God's designs, which will be accomplished, whether you hear or whether you forbear. The Lord himself; i.e. "the Lord himself, of his own free will, unasked."
Will give you a sign. "Signs" were of various kinds. They might be actual miracles performed to attest a Divine commission (Exodus 4:3-9); or judgments of God, significative of his power and justice (Exodus 10:2); or memorials of something in the past (Exodus 13:9, Exodus 13:16); or pledges of something still future.
Signs of this last-mentioned kind might be miracles ( 6:36-40; 2 Kings 20:8-11), or prophetic announcements (Exodus 3:12; 1 Samuel 2:34; 2 Kings 19:29). These last would only have the effect of signs on those who witnessed their accomplishment.
Behold. "A forewarning of a great event" (Cheyne). A virgin shall conceive. It is questioned whether the word translated "virgin," viz. 'almah, has necessarily that meaning; but it is admitted that the meaning is borne out by every other place in which the word occurs m the Old Testament (Genesis 24:43; Exodus 2:8; Psalms 68:25; Proverbs 30:19; Song of Solomon 1:3; Song of Solomon 6:8).
The LXX; writing two centuries before the birth of Christ, translate by παρθένος. The rendering "virgin" has the support of the best modern Hebraists, as Lowth, Gesenins, Ewald, Delitzsch, Kay. It is observed with reason that unless 'almah is translated "virgin," there is no announcement made worthy of the grand prelude: "The Lord himself shall give you a sign—Behold!"
The Hebrew, however, has not "a virgin," but "the virgin", which points to some special virgin, pro-eminent above all others. And shall call; better than the marginal rendering, thou shalt call. It was regarded as the privilege of a mother to determine her child's name (Genesis 4:25; Genesis 16:11; Genesis 29:32-35; Genesis 30:6-13, Genesis 30:18-21, Genesis 30:24; Genesis 35:18, etc.
), although formally the father gave it (Genesis 16:15; 2 Samuel 12:24; Luke 1:62, 83). Immanuel. Translated for us by St. Matthew (Matthew 1:23) as "God with us" ( μεθ ἡμῶν ὁ θεός). (Comp. Isaiah 8:8, Isaiah 8:10.