What is the ruling on the private parts?

The "saw'ah" (private parts) refers to the severe 'awrah (private parts) – the front and back – and it is obligatory to cover them in seclusion and in the presence of others, based on the Prophet's (peace be upon him) saying: "Guard your 'awrah except from your wife or what your right hand possesses," and "Allah, may He be blessed and exalted, is more deserving that one should feel shyness before Him."

It is obligatory to cover the 'awrah outside of prayer. The 'awrah that must be covered in seclusion for a man is only the two "saw'atan," and for a woman, it is what is between the navel and the knee.

The benefit of covering in seclusion is that Allah sees the one who covers himself as well-mannered, and leaving it uncovered is a lack of manners. It is permissible to uncover them out of necessity, such as for bathing and the like, and it is permissible to uncover them for the slightest purpose.