“I once said to abu ‘Abd Allah (a.s.), a young woman of our people has a wound in her vagina. She finds bleeding but does not know if it is because of Hayd (menses) or because of the wound and blood flows. He (the Imam) said, ‘Instruct her to lie down on her back, raise her legs and place her middle finger inside. If blood comes from the right side, it is because of Hayd (menses); if it comes from the left side, it is because of the wound.’”