The Great Canon of St. Andrew of Crete (also known as the Canon of Repentance) is a lengthy penitential canon composed in the seventh century, which is sung during Great Lent.
The Great Canon consists of four parts, each divided into nine odes. At the refrain "Have mercy on me, O God, have mercy on me," a full prostration is performed. Also, some of the odes have additional refrains and troparia to the author of the canon, St. Andrew of Crete, or St. Mary of Egypt, one of the greatest models of repentance in Christian history.
On Wednesday of the fifth week of the Great Lent, the Life of St. Mary of Egypt is read together with the entire Great Canon at Orthros.