Sahih Muslim 1086 a
Sa'd b. Abi Waqqas (Allah be pleased with him) said that the Messenger of Allah (ﷺ) struck his hand against the other and (then with the gesture of his two hands) said:
The month is thus, thus (two times). He then withdrew (one of) his fingers at the third turn.
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا مُحَمَّدُ بْنُ بِشْرٍ، حَدَّثَنَا إِسْمَاعِيلُ بْنُ أَبِي خَالِدٍ، حَدَّثَنِي مُحَمَّدُ بْنُ سَعْدٍ، عَنْ سَعْدِ بْنِ أَبِي وَقَّاصٍ، - رضى الله عنه - قَالَ ضَرَبَ رَسُولُ اللَّهِ صلى الله عليه وسلم بِيَدِهِ عَلَى الأُخْرَى فَقَالَ ‏
"‏ الشَّهْرُ هَكَذَا وَهَكَذَا ‏"‏ ‏.‏ ثُمَّ نَقَصَ فِي الثَّالِثَةِ إِصْبَعًا ‏.‏