Allah (Exalted be He) says (what means):
And (remember) when your Lord said to the angels: "Verily, I am going to place (mankind) generations after generations on earth." They said: "Will You place therein those who will make mischief therein and shed blood, - while we glorify You with praises and thanks and sanctify You." He (Allâh) said: "I know that which you do not know."
How did the angels know that these successive (mankind) generations would spread mischief on earth though no one knows the Ghayb (Unseen) but Allah?
Perhaps the angels knew that humans would make mischief and shed blood through knowledge imparted to them by Allah or by their understanding of the human nature, for Allah (Exalted be He) told them that He was creating this type of creature from sounding clay like the clay of pottery. They might have also deduced this through knowing that humans would resolve the grievances of people and deter them from committing sins or transgressing prohibitions. It was also said that the angels knew this from the deeds of other creatures that had existed on earth before Adam (peace be upon him).May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.