Angels are powerful, smart spirits that obey God's commands and praise him with singing and they have male (masculine)gender, but without any sex. They sometimes appear to humans in human form. They can deliver messages to people in person or in dreams. Angels that are named in the Bible are Michael (called a "chief prince"), Gabriel (known for telling Mary that she would be the mother of Jesus), and Raphael (in the Apocryphal Book of Tobit). The Ethiopian Book of Enoch also lists four Archangels which watch over the four quadrants of heaven; Michael, Raphael, Gabriel and Uriel. Lucifer is also known as an angel in the Bible.