The Messenger of Allah ﷺ took a bath with one Sa' of water and performed ablution with one Mudd (of water) ; and in the hadith narrated by Ibn Hujr the words are: One Mudd sufficed for his (Holy Prophet's) ablution. And Ibn Hujr said that (his Shaikh) Isma'il was much advanced in age, and it was because of this that he could not fully rely on him for this tradition.
أَبُو بَكْرٍ صَاحِبُ رَسُولِ اللَّهِ ﷺ قَالَ كَانَ رَسُولُ اللَّهِ ﷺ يَغْتَسِلُ بِالصَّاعِ وَيَتَطَهَّرُ بِالْمُدِّ وَفِي حَدِيثِ ابْنِ حُجْرٍ أَوْ قَالَ وَيُطَهِّرُهُ الْمُدُّ وَقَالَ وَقَدْ كَانَ كَبِرَ وَمَا كُنْتُ أَثِقُ بِحَدِيثِهِ