SA’. صاع or SUWA’ صواع
A certain measure used for measuring corn, and upon which depend the decisions of Muslims relating to measures of capacity. It occurs in the Qur’an, Surah xii. 72, for the drinking-cup placed by Joseph in his brother’s pack.
The compiler of the Taju ‘l-‘Arus, says that according to five different. readers of the Qur’an, it is given suwa’ in that verse! but in the majority of texts it is sa’.
The Qamus explains suwa’ as a certain vessel from which one drinks a and sa’, a measure of capacity. Its invariable measure being, according to ancient authorities, four times the quantity of corn that fills two hands of a man of moderate size.
Al-Baizawi records, besides suwa’ and sa’ the reading saw and suwagh.
Based on Hughes, Dictionary of Islam