14 Therefore the Lord himself will give you a sign. Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel. – Isaiah 7:14 ESV.
This woman must be a virgin (Isa 7:14) where it is said, ‘A virgin shall conceive, and bear a son, and shall call his name Imanuel.’ And Jesus is he that was the fulfilling of this scripture (Matt 1:22, 23), ‘Now all this was done, that it might be fulfilled which was spoken of the Lord by the prophet, saying, Behold, a virgin shall be with child, and shall bring forth a Son, and they shall call his name Imanuel.’
The Works of John Bunyan Vol. 2: Some Gospel Truths Opened (Edinburgh, London; Banner of Truth, 2009) p. 144