It wasnarrated from Muhammad bin Sa'd bin Abu Waqqas that his fathersaid:
"The Messenger of Allah (ﷺ) said: 'The month is like thatandlike that and like that,' and he showed nine fingers on thethird timeto indicate twenty-nine." (PT)
English reference (PT): Vol. 1, Book 7, Hadith 1657 (PT)
Arabic reference (PT): Book 7, Hadith 1726 (PT)