Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 214
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 214, with English translation by Maimonides (Rambam).
לשמח חתן את אשתו שנה, שנאמר: "נקי יהיה לביתו שנה אחת" (דברים כד, ה).
For a groom to rejoice together with his wife for a year, as [Deuteronomy 24:5] states: "He shall be free for his home for one year."