‘Peace be upon you’, a traditional zemer sung on Friday night at the beginning of Shabbat is believed to have been written in the 17th century, inspired by Talmudic legend. The words welcome in the two angels, one good and one evil, which are supposed to accompany a person home from synagogue on Friday night.
If there is a beautiful Shabbat feast prepared, the good angel makes a blessing that the next Shabbat will be the same and the evil angel responds ‘amen’. If there is no feast, the evil angel wishes that the next Shabbat will be the same and the good angel responds ‘amen’. Although the angels disagree with each other they respond to each other's blessing and so are known as the Messengers of Peace.