"Behold, a virgin shall conceive in the womb, and shall bring forth a son..."

The Prophet Isaiah prophesying of the Nativity of Christ from the Most-Holy Theotokos (source)

  
And the Lord again spoke to Achaz, saying,  Ask for thyself a sign of the Lord thy God, in the depth or in the height.  And Achaz said, I will not ask, neither will I tempt the Lord.  And he said, Hear ye now, O house of David; is it a little thing for you to contend with men? and how do ye contend against the Lord?  Therefore the Lord himself shall give you a sign; behold, a virgin shall conceive in the womb, and shall bring forth a son, and thou shalt call his name Emmanuel.  Butter and honey shall he eat, before he knows either to prefer evil or choose the good.  For before the child shall know good or evil, he refuses evil, to choose the good; and the land shall be forsaken which thou art afraid of because of the two kings.And the Lord said to me, Take to thyself a volume of a great new book, and write in it with a man's pen concerning the making a rapid plunder of spoils; for it is near at hand.  And make me witnesses of faithful men, Urias, and Zacharias the son of Barachias.  And I went in to the prophetess; and she conceived, and bore a son. And the Lord said to me, Call his name, Spoil quickly, plunder speedily.  For before the child shall know how to call his father or his mother, one shall take the power of Damascus and the spoils of Samaria before the king of the Assyrians. and he shall take away from Juda every man who shall be able to lift up his head, and every one able to accomplish anything; and his camp shall fill the breadth of thy land, O God with us. Know, ye Gentiles, and be conquered; hearken ye, even to the extremity of the earth: be conquered, after ye strengthened yourselves; for even if ye should again strengthen yourselves, ye shall again be conquered. And whatsoever counsel ye shall take, the Lord shall bring it to nought; and whatsoever word ye shall speak, it shall not stand among you: for God is with us.
-Isaiah 7:10-16, 8:1-4, 8-10, read at Great Vespers for the Nativity of Christ
  
(source)

 

The Prophet Isaiah prophesying of the Nativity of Christ from the Most-Holy Theotokos (source)

  

Through the prayers of our Holy Fathers, Lord Jesus Christ our God, have mercy on us and save us! Amen!