The first stage, usually at a young age, of the nuptial event: Genesis describes the betrothal and marriage of Rebecca and Rachel; the women were transposed from the custody of the father to a husband—chattels at the disposal of men. And a wedding feast duly follows (Gen. 29: 22) for ‘all the men’!
In the 1st cent. CE betrothal was still a transitional period but was binding and could only be terminated by a legal divorce. In Judaea sexual experience in this stage was common. According to Matthew and Luke Joseph was taken by surprise by Mary's pregnancy and he naturally suspected her of adultery, for which in theory the Deuteronomic law specified death by stoning. Joseph generously resolved on a private annulment in order to spare Mary publicity and penalties, but an angel intervened to assure Joseph that the condition was ‘by the Holy Spirit’ (Matt. 1: 20).
The modern custom of unmarried couples living together and intending future marriage has been likened to NT betrothal.