POLYELEOS - The Psalms of "much oil" or "many mercies" (Psalms 134-135) sung during Resurrectional and Festal Matins.
These two psalms constitute the third reading of the Psalter at Matins on Great Feasts and certain Sundays
(in some places, on all Sundays), and on all other Vigil or Polyeleos-rank feasts
. The name "polyeleos"
arises from the repetition of the phrase "for His mercy endureth forever" in Psalm 135. On the three Sundays which immediately precede Great Lent, Psalm 136
(LXX) "By the waters of Babylon..."
is added to the other two Psalms.