Prayer is the one thing that can conquer God. But Christ has willed that it should work no evil, and has given it all power over good.
Its only art is to call back the souls of the dead from the very journey into death, to give strength to the weak, to heal the sick, to exorcise the possessed, to open prison cells, to free the innocent from their chains. Prayer cleanses from sin, drives away temptations, stamps out persecutions, comforts the fainthearted, gives new strength to the courageous, brings travellers safely home, calms the waves, confounds robbers, feeds the poor, overrules the rich, lifts up the fallen, supports those who are falling, sustains those who stand firm.
All the angels pray. Every creature prays. Cattle and wild beasts pray and bend the knee. As they come from their barns and caves they look out to heaven and call out, lifting up their spirit in their own fashion. The birds, too, rise and lift themselves up to heaven: they open out their wings, instead of hands, in the form of a cross, and give voice to what seems to be a prayer.
What more need be said on the duty of prayer? Even the Lord himself prayed. To him be honor and power for ever and ever. Amen.
--Tertullian, On Prayer