Sahih Muslim Book - 13, Hadith - 2513

حَدَّثَنَا أَبُو كَامِلٍ الْجَحْدَرِىُّ حَدَّثَنَا عَبْدُ الْوَاحِدِ بْنُ زِيَادٍ حَدَّثَنَا الْحَسَنُ بْنُ عُبَيْدِ اللَّهِ عَنْ سَعْدِ بْنِ عُبَيْدَةَ قَالَ سَمِعَ ابْنُ عُمَرَ - رضى الله عنهما - رَجُلاً يَقُولُ اللَّيْلَةَ لَيْلَةُ النِّصْفِ فَقَالَ لَهُ مَا يُدْرِيكَ أَنَّ اللَّيْلَةَ النِّصْفُ سَمِعْتُ رَسُولَ اللَّهِ -صلى الله عليه وسلم- يَقُولُ « الشَّهْرُ هَكَذَا وَهَكَذَا ». وَأَشَارَ بِأَصَابِعِهِ الْعَشْرِ مَرَّتَيْنِ « وَهَكَذَا ». فِى الثَّالِثَةِ وَأَشَارَ بِأَصَابِعِهِ كُلِّهَا وَحَبَسَ أَوْ خَنَسَ إِبْهَامَهُ ».

It was narrated that Sad bin Ubaidah said: “Ibn Umar [May Allah be pleased with him] heard a man saying: ‘tonight is halfway (through the month),’ and he said to him: ‘How do you know that tonight is halfway (through the month)? I heard the Messenger of Allah (SAW) say: ‘the month is like this, and like this,’ and he showed ten with his fingers twice, “and like this,” and he showed all his fingers the third time, but he tucked away, or hid his thumb.’”