Deuteronomy 22:23-24
"If a man is discovered having relations with a woman who is married to another, both the man and the woman with whom he has had relations shall die. Thus shall you purge the evil from your midst. "If within the city a man comes upon a maiden who is betrothed, and has relations with her, you shall bring them both out to the gate of the city and there stone them to death: the girl because she did not cry out for help though she was in the city, and the man because he violated his neighbor's wife.
About as clear as it gets.
1:26 In the sixth month, God sent the angel Gabriel to Nazareth, a town in Galilee, 27 to a virgin pledged to be married to a man named Joseph, a descendant of David.
2:4 So Joseph also went up from the town of Nazareth in Galilee to Judea, to Bethlehem the town of David, because he belonged to the house and line of David. 5 He went there to register with Mary, who was pledged to be married to him and was expecting a child. 6 While they were there, the time came for the baby to be born, 7 and she gave birth to her firstborn, a son. She wrapped him in cloths and placed him in a manger, because there was no room for them in the inn.
Nelsons Bible Dictionary explains:
In biblical times, a betrothal for marriage was a binding agreement that set the young woman apart for the young man. The agreement was voided only by death or divorce; one could not get out of the betrothal in any other way. When Joseph discovered that Mary was pregnant, he did not want to make a “public example” of her; instead, he decided to divorce her secretly. However, he did not carry out the divorce, because an angel of the Lord convinced him that the baby to be born to Mary would be the Son of God (Matt. 1:18–25).During the engagement period, the bridegroom had certain privileges. If war was declared, he was exempt from military duty (Deut. 20:7). He also knew that his bride-to-be was protected by Mosaic Law. If another man raped her, the act was treated as adultery; and the offender was punished accordingly (Deut. 22:23–27). This was considered a more serious crime than the rape of a girl not yet betrothed (Deut. 22:28–29).
The length of engagement varied. Sometimes the couple was married the same day they were engaged. Usually, however, a period of time elapsed between the betrothal and the marriage ceremony. During this time the young man prepared a place in his father's house for his bride, while the bride prepared herself for married life.
On the day of the wedding, the groom and his friends dressed in their finest clothes and went to the home of the bride. Together the couple went back to the groom's house. Their friends sang and danced their way back to his house.
Once at the groom's house, the couple was ushered into a bridal chamber. The marriage was consummated through sexual union as the guests waited outside. Once that fact was announced, the wedding festivities continued, with guests dropping by for the wedding feast. Usually the wedding party lasted for a week (Gen. 29:27).