These sources accompany the second episode of the second season of the Joy of Text podcast.
A woman who has been betrothed (i.e., an arusah) is forbidden to her husband (in regards to intercourse) – according to Rabbinic law – as long as she is living in her father’s home. A man who has intercourse with his arusah in his father-in-law’s home is punished with “lashes for rebelliousness.”
Even when [the husband] betrothed her with her with an act of sexual intercourse, he is forbidden to have sexual intercourse with her a second time while she is in her father’s home until he brings her to his home, be in seclusion with her, and thus singles her out as his wife.
This seclusion is called “entering into the chuppah,” and it is universally referred to nisu’in (marriage).