The angels realized that Adam was the creature who knew what they did not know and that his capacity to learn was his noblest quality. His knowledge included knowledge of the Creator which we call Faith or Islam, as well as the knowledge that he would need to inhabit and master the earth, and all kinds of worldly knowledge which are included in this.
"When a person dies, his works end, except for three: ongoing charity, knowledge that is benefited from, and a righteous child who prays for him."
Prophet Mohammed (PBUH)
"The best of what a man leaves behind are three: a righteous child who supplicates for him, ongoing charity the reward of which reaches him, and knowledge that is acted upon after him."
Sunan Ibn Mājah
"Every day two angels come down from Heaven and one of them says, 'O Allah! Compensate every person who spends in Your Cause,' and the other (angel) says, 'O Allah! Destroy every miser.'"
Sahih Bukhari