Tafsir of Ash-Shu`ara' 26:70

(إذ قال) is in the accusative case as an adverbial of time for "a narrative" (naba’), according to the view held by Abu al-Baqa’; meaning: [Relate to them] the narrative at the time of his saying to his father and his people. Or it is in the accusative case as the object of "recite" (utlu), being a substitute for "the narrative," as implied by the words of al-Hawfi; meaning: recite to them the time of his saying to them: "What do you worship?" on the basis that what is being recited is what the Prophet—peace be upon him—said at that time.

The pronoun in (his people) refers back to Abraham. It is also said: it refers back to his father, in order to accord with His saying—Exalted is He—: "Indeed, I see you and your people in clear error." However, this necessitates a disconnection [of the pronoun’s referent].

He—peace be upon him—asked them about what they worship in order to build upon their answer that what they worship is entirely devoid of any worthiness of worship, not for the sake of inquiry, as that was already known and observed by him—peace be upon him.