"Indeed, in that"—meaning in the affair of the people of Noah and their drowning—"are signs" for those who come after them. "And indeed, We were testing [them]"—meaning, by what the Messengers were sent with regarding His worship. The meaning of 'al-ibtila' (testing) is trial (al-ikhtibar).

Surah Al-Mu'minun from (verse 31 to verse 41).