“Look! The virgin will conceive a child! She will give birth to a son, and they will call Him Immanuel, which means God with us.”
There were three steps in a Jewish marriage in the time period when the Lord Jesus was born. First the families agreed to the marriage. Secondly an announcement would be made and the couple would be engaged – to break an engagement death or divorce would need to occur. Then the couple would be married and would live together. Joseph did not want to disgrace Mary because she was pregnant and wanted to divorce her and break their engagement. As he pondered this – and angel of the Lord appeared to him. God sent down one of His angels to explain to Joseph what had happened and to tell him to take Mary as his wife. Because Jesus was born of a virgin and was the Son of God, He was born without human sin. The prophecy of Isaiah was fulfilled in Jesus birth.
Therefore Go! (and make disciples of all nations)