The angel sent by God to bring about death is known as malakh ha-mavet in Hebrew. There are no references in the Bible to a specific angel of death but the concept is found frequently in rabbinic literature and in Jewish folklore.
In the latter, for instance, the practice of pouring out all the water in pots and so forth when a death occurs is said to be based on the belief of that the Angel of Death dips his sword in the water and poisons it. Maimonides (Guide of the Perplexed, 3. 22) demythologizes the concept, understanding it as the life-denying, evil force that lurks in the human psyche. Maimonides quotes with much approval the Talmudic saying (tractate Bava Batra 16a) that Satan, the evil inclination, and the Angel of Death are one and the same. In Yiddish slang a man with destructive tendencies or one who is always running down others is called an Angel of Death.
Reprinted from The Jewish Religion: A Companion, published by Oxford University Press.