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." (ID)
English reference (ID): Vol. 1, Book 7, Hadith 1657 (ID)
Arabic reference (ID): Book 7, Hadith 1726 (ID)