John Chrysostom

Then Paul having taken brushwood, laid it on the fire. See how active he is; observe how we nowhere find him doing miracles for the sake of doing them, but only upon emergency. Both during the storm when there was a cause he prophesied, not for the sake of prophesying, and here again in the first instance he lays on brushwood: nothing for vain display, but with a simple view to their being preserved, and enjoying some warmth.

Homily on Acts 54 ↗

Basil of Caesarea

Beasts bear witness to the faith. Hast thou confidence in the Lord? "Thou shalt walk upon the asp and the basilisk and thou shalt trample under feet the lion and the dragon." With faith thou hast the power to walk upon serpents and scorpions. Do you not see that the viper which attached itself to the hand of Paul, whilst he gathered sticks, did not injure him, because it found the saint full of faith? If you have not faith, do not fear beasts so much as your faithlessness, which renders you susceptible of all corruption.

Homilies On The Hexaemeron 9.6 ↗

Theophylact of Ohrid

When Paul was gathering brushwood, a viper bit his hand and caused him no harm, because the holy man was a practitioner of faith. Having sunk its fangs into the apostle's hand and finding no sinful wound in it, the viper immediately recoiled and threw itself into the fire, as if seeking punishment for itself. We, however, fear wild beasts, since we do not possess the full armor of virtue.

Commentary on Acts ↗

Bede

When Paul had gathered a great bundle of sticks and laid them on the fire. The Apostle, having come out of the sea, kindled a fire because of the cold, as he warmed the hearts of those he had rescued from the tempests by his teaching with the ardor of love. The sticks are called any exhortations, which, capable of kindling charity, are as if cut from the integrity of the Scriptures, like branches cut with leaves.

Commentary on Acts ↗