Church Fathers on Luke 17:9

Because faith makes its possessor a keeper of God’s commandments, and adorns him with wonderful works; it would seem from thence that a man might thereby fall into the sin of pride. Our Lord therefore forewarned His Apostles by a fit example, not to boast themselves in their virtues, saying, But which of you having a servant plowing, &c.

Or else; To the many who understand not this faith in the truth already present, our Lord might seem not to have answered the petitions of His disciples. And there appears a difficulty in the connection here, unless we suppose He meant the change from faith to faith, from that faith, namely, by which we serve God, to that whereby we enjoy Him. For then will our faith be increased when we first believe the word preached, next the reality present. But that joyful contemplation…

Or the servant departs from the field when giving up for a time his work of preaching, the teacher retires into his own conscience, pondering his own words or deeds within himself. To whom our Lord does not at once say, Go from this mortal life, and sit down to meat, that is, refresh yourself in the everlasting resting-place of a blessed life.