Patristic Wisdom: Looking to the Fifteenth Sunday after Pentecost

Your testimonies are wonderful.
        On account of this, my soul examined them.
The revelation of your words will give light
        and instruct infants.
I opened my mouth and excited a spirit,
        because I was desiring your commandments.
Look upon me, and have mercy upon me,
        according to the justice of those who love your name.
Make my steps straight according to your word,
        and do not let any lawlessness have dominion over me.
Redeem me from the false accusation of people,
        and I will keep your commandments.
Show forth your face upon your servant,
        and teach me your righteous ordinances.
My eyes were traversed with streams of waters,
        since they did not keep your law.

(Ps 118:129–136 LXX [Ps 119:129–136])

I opened my mouth and drew in breath, because I longed for thy commandments. If you are attracted to a literal interpretation here, it explains the tendency of a speaker. First the mouth is opened, the breath is drawn in, and then the tongue is moved to allow the voice to sound forth. But if you interpret spiritually, as you should, the mouth connotes the entry to the mind which is opened when we hasten to learn something. It draws in breath when by the divine gift it is filled with a spirit of wholesome longing, and begins with constant heart to seek what previously it was known to have sought only through God’s grace. So the weak little ones opened their mouths and drew in breath, in other words, strength for action, which they could not attain of their own accord. So that you may better realize that this first part is addressed to the good of the understanding rather than to the function of speaking, there follows: Because I longed for thy commandments. They first expressed zeal of will, to explain later their longing for the commandments; the sequence could not be logical if they said that they would first speak and then long for what was to their benefit.

Direct my steps according to thy word, and let not any iniquity have dominion over me. My steps denotes movements of the soul, for just as by our steps we move from place to place, so by those paces of the soul, so to speak, we advance to things better or worse. The blessed troop asked that these steps be directed according to the Lord’s word, so that they should not be seduced by evil vices, and slip into deadly errors. According to thy word means “according to the commands which You lay down for improving the life of the human race.” Next comes: And let not any iniquity have dominion over me. It was essential that if the Lord were to deign to direct their steps according to His word, no iniquity should prevail over them, for it could not be so utterly banished that it could not assault them further. But when it does not prevail, we escape it, whereas slavery to it consigns us down to destruction. The phrase, any iniquity, is not idle, for they know that if it prevails over them at any point, it carries them off, and it is no use keeping the Law in many matters if we are seen to transgress it in any respect. Scripture says: If anyone keeps the whole law but offends in one point, he becomes guilty in all.

Cassiodorus, Explanation of the Psalms 118.131, 133