A moving prayer, describing the awe of the Day of Judgement, that is recited on the High Holy Days before Kedusha of Mussaf. According to a tradition cited in Sefer Ohr Zarua, R' Ephraim of Bonn attributed it to an 11th century German sage by the name of R' Amnon of Mainz (Mayence), who composed it after sanctifying God's name by rejecting a demand by the local bishop that he convert to Christianity. However, modern scholars believe that it is of much earlier composition, as fragments of the prayer were found in the Cairo Geniza dating to the 8th Century. Some researchers believe that it was composed by Yannai in the sixth century.