Basil of Caesarea

There are three different distinct kinds of obedience. For either from fear of punishment we avoid evil and are servilely disposed; or looking to the gain of a reward we perform what is commanded, like to mercenaries; or we obey the law for the sake of good itself and our love to Him who gave it, and so savour of the mind of children.

Catena Aurea by Aquinas ↗

Bede

And I am no longer worthy to be called your son. Treat me as one of your hired servants. Indeed, he does not dare to aspire to the affection of a son, who does not doubt that all things which are of the father are his own, but he desires the status of a hired servant, now willing to serve for a wage. Yet he testifies that he can merit even this only by paternal grace. Where then are the Pelagians, who trust that they can be saved by their own virtue, against the very clear sentence of truth which says: Without me, you can do nothing?

On the Gospel of Luke ↗

Bonaventure

And because an offense against such great majesty deprives us of the dignity of divine filiation, he therefore confesses his own unworthiness, when he adds: Now I am not worthy to be called your son: and this indeed he confesses rightly and truly, because to be a son of God belongs to the greatest charity, according to that passage in 1 John 3: "See, brethren, what manner of charity the Father has given us, that we should be called and should be sons of God." Of this name the sinner is unworthy, because he despised his Father, …

Commentary on Luke, Chapter 15 ↗