When is marriage first mentioned in the bible?

The very first marriage in The Bible was between Adam and Eve. Although the Word marriage was not used, it says in Gen 2:24: "Therefore a man will leave his father and his mother, and will join with his wife, and they will be one flesh." The Hebrew Word used "wife" is defined as woman, wife (married to a man), female. The verse actually describes what marriage is: the joining of a man and a woman to create a new entity or family.

Genesis 29:18-30 describes Jacob betrothal to Rachel.

Laban replied, "It is not our custom here to give the younger daughter in marriage before the older one." Gen 29:26.