SAA or SA’
Saa is an Arabic word. A Propheticsaa’ ( صاع) is not a weight measurement. It was and still is a measurement of volume, similar to the size of a large salad bowl. It is made up of four mudds, and a mudd ( مد ) is a smaller container, close to the size of a small salad bowl.
To be precise, a Prophetic mudd in modern volume measurements is .75Litre (or 750mL), which means that a saa’ is three litres.
In one narration of the hadeeth, the Prophet (may Allaah raise his rank and grant him peace) said when praying for Allaah to bless the mudd and the saa’: (what means), “blessings upon blessings.” Sahih Muslim 1368 (Book 7, Hadith 3161)
Abu Sa’eed al-Khudri (may Allaah be pleased with him) said: “We used to pay as Zakaat al-Fitr a sa’ of food or a sa’ of barley (which was their food at that time) or a saa’ or dates or a sa’ of aqit (dried yoghurt) or a saa’ of raisins(dried grapes).” Sahih al-Bukhari 1506(Vol.2: 282) and Sunan an-Nasa'i Vol. 3: 2512
Narrated Ibn `Umar(R):Allah's Messenger (ﷺ) enjoined the payment of one Sa' of dates or one Sa' of barley as Zakat-ul-Fitr on every Muslim slave or free, male or female, young or old, and he ordered that it be paid before the people went out to offer the `Id prayer. Sahih al-Bukhari 1503 (Vol.2 : 579)
Al-’Allaamah al-Laknawee (may Allaah have Mercy on him) – a former teacher at the Haram in Makkah and at Daar al-Hadeeth, an Indian scholar grounded in Tawheedand firm against the people of desires – said about this mudd: This is the mudd that the Prophet (may Allaah raise his rank and grant him peace) was speaking about when he prayed, “O Allaah! Put blessings in our saa’ and our mudd!” This was collected by the two shaykhs (al-Bukhaaree and Muslim). Further, he (may Allaah raise his rank and grant him peace) used to make wudhoo’ using this mudd, and he used to take a bath using a saa’. An-Najm al-Baadee, Shaykh Yahyaa al-Mudarris’ biography (p.63)