Tafsir of Luqman 31:3

(A guidance and a mercy) in the accusative case as a hal (state) of the word "the verses," and the operative factor in them is the meaning of the indication, as mentioned by more than one scholar, though this has been debated.

Hamzah, al-A'mash, al-Za'farani, Talhah, and Qunbul—from the transmission of Abu al-Fadl al-Wasiti and Nazif—read it in the nominative case as a predicate following a predicate, according to the school of the majority, or as a predicate for an implied subject, meaning: "They are," or "It is, a great guidance and mercy."

(For the doers of good) meaning: those who perform good deeds. The prepositional phrase is connected to an implied word serving as an adjective for the two conjoined nouns. And His saying, the Exalted: