We are an unlettered people who can neither write nor count. The month is thus, and thus. folding his thumb when he said it the third time.
Sahih Muslim Book 13, Hadith 17
← Previous Hadith The month (of Ramadan) may consist of twenty nine days, and Shu'ba (one of the narrators) (gave a practical demonstration how the Holy prophet (ﷺ) explained to them) by unfolding his hands thrice and folding his thumb at the third turn. 'Uqba (one of the narrators in this chain of transmitters) said: I think that he said that the month consists of thirty days and unfolded his palm three times.

Sahih Muslim Book 13, Hadith 16 Next Hadith → This hadith has been narrated on the authority of Aswad b. Qais with the same chain of transmitters, but herein no mention has been made of the other month (consisting of) thirty days.

Sahih Muslim Book 13, Hadith 18