John Cassian, Conferences I–X IX.20: Of the clause “Thy will be done.”

The third petition is that of sons: “Thy will be done as in heaven so on earth.” There can now be no grander prayer than to wish that earthly things may be made equal with things heavenly: for what else is it to say “Thy will be done as in heaven so on earth,” than to ask that men may be like angels and that as God’s will is ever fulfilled by them in heaven, so also all those who are on earth may do not their own but His will? This too no one could say from the heart but only one who believed that God disposes for our good all things which are seen, whether fortunate or unfortunate, and that He is more careful and provident for our good and salvation than we ourselves are for ourselves. Or at any rate it may be taken in this way: The will of God is the salvation of all men, according to these words of the blessed Paul: “Who willeth all men to be saved and to come to the knowledge of the truth.” Of which will also the prophet Isaiah says in the Person of God the Father: “And all Thy will shall be done.” When we say then “Thy will be done as in heaven so on earth,” we pray in other words for this; viz., that as those who are in heaven, so also may all those who dwell on earth be saved, O Father, by the knowledge of Thee.