How did Iblis know that Adam would have offspring, given that his statement — "Because You have put me in error, I will surely sit in wait for them on Your straight path. Then I will come at them from before them and from behind them and on their right and on their left, and You will not find most of them grateful" — was made before Adam and Eve were expelled from Paradise and before Eve became pregnant?

Allah Almighty informed us that He would place a khalifa (vicegerent) on Earth, meaning peoples who would succeed one another. It appears that khalifa does not refer to Adam alone, but also to his descendants, as evidenced by the angels' question: "Will You place upon it one who causes corruption therein and sheds blood?" (Qur'an 2:30). They knew that some of Adam's descendants would cause corruption. The angels' question was for inquiry about wisdom, not for objection or envy. So, Allah answered them: "Indeed, I know that which you do not know" (Qur'an 2:30), meaning that He knows the prevailing benefit in their creation due to the presence of prophets, the truthful, and the righteous among them.