Sunan an-Nasa'i 4311

It was narrated that Ibn Al- Hawtakiyyah said:"Umar, May Allah be pleased with us on the day when we stopped at Al-Qaha?' Abu Dharr said: 'I was. A rabbit was brought to the Messenger Allah and the man who brought it said: I saw it bleeding (menstruating). The Prophet did not eat, then he said: "Eat." A man said: "I am fasting." He said: "What fast are you observing?" He said: "Three days each month" He said: "Why don't yo