Hadith 38

وعن عبد الله بن زيد قال: أن النبي صلى الله عليه وآله وسلم أتي بثلثي مد فجعل يدلك ذراعيه . أخرجه أحمد ،‏‏‏‏ وصححه ابن خزيمة.
Narrated ‘Abdullah bin Zaid (rad): Two thirds of a Mudd (of water) was brought to he Prophet (ﷺ) (for ablution) so he began rubbing his arms. [Reported by Ahmed, and Ibn Khuzaima graded it Sahih].
Hadith Reference بلوغ المرام / 38
Hadith Grading محدثین: صحيح
Hadith Takhrij «أخرجه أحمد: 4 / 39، وابن خزيمة:1 / 62، حديث:118 واللفظ له، وصححه ابن حبان( الموارد)، حديث:155، والحاكم: 1 / 144و 162،161 علي شرط الشيخين، ووافقه الذهبي.»
Explanation & Benefits
Shaykh Safi ur-Rahman Mubarakpuri
Lexical Explanation:
«أُتِيَ» is a passive verb whose attribution is towards the object.
«مُدٍّ» is pronounced with a dammah on the "meem" and a shaddah on the "dal". It is a vessel for water in which one ratl and a third of a ratl of water fits. In contemporary terms, this amounts to eight hundred milliliters.
«يَدْلُك» means to wash while rubbing.
«ذِرَاعَيْهِ» refers to the part from the palm to the elbow, i.e., the hand. The meaning is that the Prophet sallallahu alayhi wa sallam performed ablution (wudu) with this amount of water. This is the minimum amount of water reported from the Prophet sallallahu alayhi wa sallam regarding ablution, that he used this much water for ablution.

Benefits and Issues:
➊ The hadith regarding the amount of two-thirds of a mudd is authentic. And it is in Bukhari and Muslim that the Noble Prophet sallallahu alayhi wa sallam performed ablution (wudu) with one mudd. [صحيح البخاري، الوضوبالمد، حديث 201۔ و صحيح مسلم۔ الحيض حديث 325]
➋ The Hijazi mudd is slightly less than the English seer. There are four mudds in one sa’ (saa’), and one sa’ according to current measurements is three liters and two hundred milliliters. Accordingly, one mudd will be three hundred and thirteen grams (approximately twelve chhatank). From this, it is understood that one should avoid using more water than necessary.
Source: Bulugh al-Maram: Commentary by Safiur Rahman Mubarakpuri, Page: 38