Ibn 'Umar (may Allah be pleased with both of them) reported Allah's Apostle ﷺ as saying: 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. 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.

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا غُنْدَرٌ، عَنْ شُعْبَةَ، ح وَحَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، وَابْنُ بَشَّارٍ قَالَ ابْنُ الْمُثَنَّى حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، عَنِ الأَسْوَدِ بْنِ قَيْسٍ، قَالَ سَمِعْتُ سَعِيدَ بْنَ عَمْرِو بْنِ سَعِيدٍ، أَنَّهُ سَمِعَ ابْنَ عُمَرَ، - رضى الله عنهما - يُحَدِّثُ عَنِ النَّبِيِّ ﷺ قَالَ
" إِنَّا أُمَّةٌ أُمِّيَّةٌ لاَ نَكْتُبُ وَلاَ نَحْسُبُ الشَّهْرُ هَكَذَا وَهَكَذَا وَهَكَذَا - وَعَقَدَ الإِبْهَامَ فِي الثَّالِثَةِ - وَالشَّهْرُ هَكَذَا وَهَكَذَا وَهَكَذَا " . يَعْنِي تَمَامَ ثَلاَثِينَ .