Answered by Shaykh Sohail Hanif, SunniPath Academy Teacher
Is it necessary for a woman to repeat her namaz if a strand of her hair pokes out from under her covering, even if she did not notice it until after she finished praying?
Both women and men are obliged to cover their nakedness (awra) during the prayer. The nakedness of a woman is all of her body except her face, hands and feet whilst the nakedness of a man is from his navel to his knees.
However, if a small part of one’s nakedness shows such as a few strands of hair, one’s prayer is not rendered invalid. Up to a quarter of a body part may show without the prayer being rendered invalid; beyond this, the prayer is invalid. Please see the link below for a detailed explanation of this.