The Exaltation of the Precious Cross of Christ (source)
We venerate the wood of Your Cross, O humane One, for You, the Life of all, were nailed to it. O Savior, You opened Paradise to the Robber who approached You with faith. He was counted worthy of delight, confessing You, Remember me, O Lord. Accept us as You accepted him, for we now cry, We all have sinned against Your compassion. Do not abandon us.
-Kathisma from the Feast of the Holy Cross
(source)
Through the prayers of our Holy Fathers, Lord Jesus Christ our God, have mercy on us and save us! Amen!