وَأَصْحَٰبُ ٱلْيَمِينِ مَآ أَصْحَٰبُ ٱلْيَمِينِ
This verse repeats the pattern of the eighth verse exactly: a noun + mā + the same noun. The function of the pattern was dealt with at the eighth verse and will not be repeated here.
But something has changed, and the matter pointed to in the section The structure of the sūra meets us here:
What is the difference? Maymana is on the mafʿala pattern, and in Arabic this pattern conveys place or time: the right side, the right flank. Yamīn, on the other hand, is directly the name of a hand or of a direction.
I give the distinction that may be drawn from this as my own reading and do not count it certain: in the opening section (7-11) people were being divided into sides — there was an act of division there, and so a word conveying place was suitable. In the section of tables it is no longer sides but identity that is being described.
1. The right side — al-yamīn, the right hand. 2. Blessing, good fortune — yumn (blessing), maymūn (fortunate).
The joining of the two senses is a cultural datum: the right hand is the hand with which most work is done, and from this the sense "fortunate, good" arose. Mashʾama (the left) is from the same root as shuʾm (ill omen).
And this calls for a caution: the verses issue no ruling about a hand or a direction. The words are taken from a pair ready to hand in the hearer's language. The measure recorded in several places earlier in this commentary holds here too: the Qurʾān uses the hearer's vocabulary; it is not obliged to endorse that vocabulary.