Jesus would be born of a Virgin.

Prophecy: "Therefore the Lord Himself shall give you a sign, Behold, the young woman who is unmarried and a virgin shall conceive and bear a son, and shall call his name Immanuel-God with us (Isaiah 7:14).

Fulfilment: "Now the birth of Jesus Christ took place under these circumstances:

When His mother Mary had been promised in marriage to Joseph, before they came together she was found to be pregnant (through the power) of the Holy Spirit" (Matthew 1:18 ).