John Chrysostom

But mark both their faith, and their obedience. For though they were in the midst of their work (and ye know how greedy a thing fishing is), when they heard His command they delayed not, they procrastinated not, they said not, "let us return home, and converse with our kinsfolk," but "they forsook all and followed," even as Elisha did to Elijah. Because such is the obedience which Christ seeks of us, as that we delay not even a moment of time, though something absolutely most needful should vehemently press on us. …

Homily on the Gospel of Matthew 14 ↗

Gregory the Dialogist

Peter and Andrew had seen Christ work no miracle, had heard from him no word of the promise of the eternal reward, yet at this single bidding of the Lord they forgot all that they had seemed to possess, and straightway left their nets, and followed Him. In which deed we ought rather to consider their wills than the amount of their property. He leaves much who keeps nothing for himself, he parts with much, who with his possessions renounces his lusts. …

Catena Aurea by Aquinas ↗

Thomas Aquinas

Their obedience is indicated, when he says immediately they left their nets and followed him. He indicates their obedience in regard to three things: First, as to promptness: "Do not postpone from day to day" (Sir 5:7); "But when he who had set me apart before I was born, and had called me through his grace..., I did not confer with flesh and blood" (Gal 1:15); "The Lord God has opened my ear, and I was not rebellious, I turned not backward" (Is 50:5). …

Commentary on Matthew ↗