Is it necessary to wear one’s shirt outside one’s pants?

Regarding men wearing western style shirt and pants: Is it permissible for the male to wear his shirt tucked inside of his pants or should he allow the tail of the shirt to hang loosely on the outside covering the private parts ?

Praise be to Allah, and blessings and peace be upon the Messenger of Allah:

If the trousers contain nothing haraam and are loose and do not reveal the shape of the private parts, there is nothing wrong with tucking the shirt into the pants, but if they are tight around the area of the private parts, it is necessary to cover that with the shirt or with something else.

And Allaah knows best.