What is the evidence that a man's awrah (private parts) is what is between the navel and the knee? And what is the evidence that a woman's awrah in front of her maharim (unmarriageable kin) is what is between the navel and the knee? And why must a woman cover her entire body during prayer and not suffice with covering what is between the navel and the knee?

A man's 'awrah (intimate parts) is what is between the navel and the knee in all situations; the navel and the knee themselves are not part of the 'awrah. A woman's 'awrah during prayer is her entire body except for her face and palms. As for her 'awrah in front of her mahrams (unmarriageable kin), there is a difference of opinion: some scholars hold that it is what is between the navel and the knee, while others hold that it is everything except what normally appears, such as the face, head, hands, and feet. However, in front of non-mahram men, her entire body is 'awrah.