"The month is like this," and (one of the narrators) Shubah did the same gesture as Jabalah had done, copying, Ibn 'Umar: "It is twenty-nine, as he gestured twice with all fingers of both hands, and putting down one of his fingers the third time."
Sunan an-Nasa'i Book 22, Hadith 53
← Previous Hadith he heard Ibn 'Umar narrate that the Prophet said; "We are an unlettered Ummah; we do not use computation. The month is like this, and this, and this," and he held down his thumb the last time. "And the month is like this, and this, and this," completing thirty.

Sunan an-Nasa'i Book 22, Hadith 52 Next Hadith → "The Messenger of Allah said: "The month is twenty-nine (days)."

Sunan an-Nasa'i Book 22, Hadith 54