'Regulation' in the Bible

During the year before each young woman’s turn to go to King Ahasuerus, the harem regulation required her to receive beauty treatments with oil of myrrh for six months and then with perfumes and cosmetics for another six months.

the Jews established and made a custom for themselves and for their descendants and for all those who allied themselves with them, so that they would not fail to celebrate these two days according to their regulation and according to their appointed time annually.