It's like they say about drinks for an alcoholic: One is too many, 84 aren't enough:
Police in northern Nigeria have arrested a Muslim preacher who claims 86 wives and 107 children, charging him with breaking Islamic laws governing marriage.
[. . .]
It was unclear when the man would appear before the court, or what the potential punishment could be. Muslim principles forbid men to take more than four wives.
Why four, I wonder, instead of three or five or six? What's the religious magic of four? And up to four wives are allowed only if the husband can "deal justly" with them