(13) باب قَوْلِ النَّبِيِّ صلى الله عليه وسلم " لاَ نَكْتُبُ وَلاَ نَحْسُبُ ".
Narrated Ibn `Umar:
The Prophet (ﷺ) said, "We are an illiterate nation; we neither write, nor know accounts. The month is like this and this, i.e. sometimes of 29 days and sometimes of thirty days." (RU)
Reference (RU): Sahih al-Bukhari 1913 (RU)
In-book reference (RU): Book 30, Hadith 23 (RU)
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 31, Hadith 137 (RU)