حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ حَدَّثَنَا شُعْبَةُ عَنْ جَبَلَةَ سَمِعْتُ ابْنَ عُمَرَ يَقُولُ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ الشَّهْرُ هَكَذَا وَطَبَّقَ أَصَابِعَهُ مَرَّتَيْنِ وَكَسَرَ فِي الثَّالِثَةِ الْإِبْهَامَ يَعْنِي قَوْلَهُ تِسْعٌ وَعِشْرُونَ
مسند امام احمد بن حنبل · Hadith 5536
It was narrated from Jabalah: I heard Ibn 'Umar say: The Messenger of Allah (PBUH) said: "The month is like this," and he clapped his hands twice, then tucked away his thumb cm the third time, meaning: twenty-nine (days).
Sanad
حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ حَدَّثَنَا شُعْبَةُ عَنْ جَبَلَةَ سَمِعْتُ ابْنَ عُمَرَ