Tafsir of Al-Anbiya' 21:62

(They said) is an incipience (isti'naf) built upon a question arising from the narration of their statement, as if it were asked: "What did they do with him after that? Did they bring him [before them] or not?" Thus, it was said: "They said, 'Have you done this to our gods, O Abraham?'"

This is an abbreviation, limited to narrating their addressing him, peace be upon him, to alert [the reader] that their bringing him and their haste to do so is a confirmed matter that requires no explanation. The hamza, as the scholar al-Taftazani stated, is for seeking an admission of the doer; for the intent of the disbelievers was not to urge him, peace be upon him, to specify [who did it]—since the breaking of the idols had already occurred—but rather it was to secure an admission that it was from him. How could it be otherwise, when they pointed to the act in their saying, "Have you done this?" And furthermore...