'I have sighted the crescent.' He said: 'Do you bear witness that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger?' He said: 'Yes.' So the Prophet gave the call saying: 'Fast."'
Sunan an-Nasa'i Book 22, Hadith 23
← Previous Hadith "I came to Ash-Sham. He said: "I came to Ash-Sham and complete her errand. Then the new crescent of Ramadan was sighted while I was in Ash-Sham. I saw the new crescent on the night of Friday, then I came to Al-Madinah at the end of the month. 'Abdullah bin 'Abbas asked me about the sighting of the moon and said: ' When did you see it?' I said: 'We saw it on the night of Friday.' He said; 'You saw it on the ninth of Friday?' I said: 'Yes, and the people saw it and started fasting, and so did Muawiyah. He said: 'But we saw it on the night of Saturday, so we will continue fasting until we have completed thirty days or we see it.' I said: 'Will you not be content with the sighting of Muawiyah and his companions? He said; 'No; this is what the Messenger of Allah enjoined upon us."'

Sunan an-Nasa'i Book 22, Hadith 22 Next Hadith → "A Bedouin come to the Prophet and said; 'I have sighted the crescent tonight.' He said: 'Do you bear witness that there is none worthy of worship except Allah, and that Messenger?' He said: 'Yes.' He said: 'O Bilal, announce to the people that they should fast tomorrow. "'

Sunan an-Nasa'i Book 22, Hadith 24