Abdullah bin Abbas (may Allah be pleased with them both) narrates: A Bedouin came to the service of the Prophet (peace be upon him) and said: I have seen the new moon of the first (of the month). The Prophet (peace be upon him) asked: "Do you bear witness that there is no deity except Allah and that Muhammad (peace be upon him) is the Messenger of Allah?" He replied: Yes! So the Prophet (peace be upon him) announced that the people should fast.