"The Messenger of Allah said to a woman from among the Ansar: 'When it is Ramadan, perform 'Umrah then, for 'Umrah during it is equivalent to Hajj."
Sunan an-Nasa'i Book 22, Hadith 21
← Previous Hadith 'I fasted Ramadan' or 'I prayed Qiyam throughout the whole month."' I do not know whether he dislike self-praise or he said: "Inevitably there will be heedlessness and sleep." (Da 'if)

Sunan an-Nasa'i Book 22, Hadith 20 Next 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