In the Law of Moses mourning was traditionally seven days, though sometimes it was a lot longer. When Moses died the people mourned for 30 days. When Jacob thought Joseph had died, he ripped his clothes off mourned for his son for 30 days. Mourning was intense and ritualistic back then. Dancing was also associated with many traditions, they would only dance certain dances and only on certain occasions that the law of Moses told them they could. So both mourning and dancing were rarely done back then.
