Sahih al-Bukhari 7330
Sahih al-Bukhari · Book 96: Holding Fast to the Qur'an and Sunnah · The religious learned men should not differ
Narrated As-Sa'ib bin Yazid:
حَدَّثَنَا عَمْرُو بْنُ زُرَارَةَ ، حَدَّثَنَا الْقَاسِمُ بْنُ مَالِكٍ ، عَنِ الْجُعَيْدِ ، سَمِعْتُ السَّائِبَ بْنَ يَزِيدَ ، يَقُولُ كَانَ الصَّاعُ عَلَى عَهْدِ النَّبِيِّ صلى الله عليه وسلم مُدًّا وَثُلُثًا بِمُدِّكُمُ الْيَوْمَ ، وَقَدْ زِيدَ فِيهِ. سَمِعَ الْقَاسِمُ بْنُ مَالِكٍ الْجُعَيْدَ
The Sa' (a kind of measure) during the lifetime of the Prophet (ﷺ) used to be equal to the one Mudd (another kind of measure) and one third of a Mudd which we use today, but the Sa' of today has become large.