Sunan an-Nasa'i 2116

It was narrated that:'Abdur-Rahman bin Zaid bin Al-Khattab addressed the people on the day concerning which there was doubt (as to whether the month had begun) and said: "I sat with the Companions of the Messenger of Allah and asked them, and they a narrated that the Messenger of Allah said: 'Fast when you see it and stop fasting when you see it, and perform the rites on that basis. If it is obscured, then complete thirty days, and if two witnesses testify then fast and stop fasting