Tafsir of Az-Zumar 39:50

(Those before them had already said it)

The pronoun in "said it" (qālahā) refers to His saying: "It was only given to me on account of knowledge." This is because it is a word or a sentence. It has been read in the masculine form (qālahū), meaning the aforementioned statement or speech. "Those before them" refers to Qarun and his people, for he said it and they were pleased with it. Thus, the attribution is a case of attributing that which belongs to a part to the whole, which is a rhetorical metaphor (majāz ‘aqlī).

It is also permitted that the metaphor lies in the prepositional phrase, such that "those before them said it" means it became widespread among them. The former interpretation is more prevalent. The intent is that they said a statement similar to this statement, or they said it exactly; because of the unity of the form of the expression, it is considered as one thing by convention.

(So, that which they used to earn did not avail them at all)

(Of the enjoyment of the world, and what they used to hoard of it.)