Tafsir of Ad-Dhariyat 51:46

"And the people of Noah": Meaning, and We destroyed [them]. For what precedes it indicates this. Or [it means], "And remember." It is said: It is a conjunction to the pronoun in "So the thunderbolt took them," and it is said: in "So We cast them into the sea," because the meaning of both is "We destroyed them," and this is as you see [i.e., questionable]. It is permitted that it be a conjunction to the place of "And in 'Ad" or "in Thamud," and it is supported by the recitation of ‘Abdullah, Abu ‘Amr, Hamzah, and al-Kisa’i of "Qawmi" (the people of Noah) in the genitive case. ‘Abd al-Warith, Mahbub, and al-Asma‘i, on the authority of Abu ‘Amr, as well as Abu al-Summal and Ibn Miqsam, recited "Qawmu" in the nominative case. The apparent meaning is that it is an inception (beginning of a sentence), and the predicate is omitted, meaning: "We destroyed them."

"From before": Meaning, before these who were destroyed.

"Indeed, they were a people defiantly disobedient": [Meaning] those who stepped outside the boundaries regarding what they were in of disbelief and acts of disobedience.