Albert Barnes Commentary Acts 28:4

"And when the barbarians saw the [venomous] creature hanging from his hand, they said one to another, No doubt this man is a murderer, whom, though he hath escaped from the sea, yet Justice hath not suffered to live." — Acts 28:4 (ASV)

The venomous beast. We usually apply the word "beast" to an animal of larger size than a viper. But the original word—thērion—is applicable to animals of any kind and is especially applied by Greek writers to serpents. See Schleusner.

No doubt. The fact that the viper had fastened on him, and that, as they supposed, he must now certainly die, was the proof from which they inferred his guilt .

Is a murderer. Why they thought he was a murderer rather than guilty of some other crime is not known. It might have been for one of the following reasons:

1. Because they inferred that he must have been guilty of some very atrocious crime; and as murder was the highest crime a person could commit, they inferred that he had been guilty of this.
2. More probably, they held the opinion that when divine vengeance overtook a person, they would be punished in a manner similar to the offense. Since murder is usually committed with the hand, and the viper had fastened on Paul’s hand, they inferred that he had been guilty of taking life. It was supposed among the ancients that individuals were often punished by divine vengeance in that part of the body which had been the instrument of the sin.

Whom, though he hath escaped the sea. They supposed that vengeance and justice would still follow the guilty; that though he might escape one form of punishment, he would yet be exposed to another. And this, to a certain extent, is true. These barbarians reasoned from great original principles, written on the hearts of all people by nature: that there is a God of justice, and that the guilty would be punished.

They reasoned incorrectly, as many do, because they supposed that every calamity is a judgment for a particular sin. People often draw this conclusion, supposing that suffering can be traced to a specific crime and should be regarded as a direct judgment from heaven (compare to John 9:1-3, and see Barnes' commentary on these verses).

The general proposition that all sin will be punished at some time is true, but we are not always qualified to affirm that particular calamities are direct judgments for sin. In some cases, we may. For instance, in the case of the drunkard, the gambler, and the profligate, we cannot doubt that the loss of property, health, and reputation is the direct result of specific crimes.

In the ordinary calamities of life, however, it requires a more profound understanding of the principles of divine government than we possess to affirm that each instance of suffering is a particular judgment for some crime.

Yet vengeance. Dikē (Justice) was represented by the pagans as a goddess, the daughter of Jupiter, whose office it was to take vengeance or inflict punishment for crimes.

Suffereth not to live. They regarded him as already a dead man. They supposed the effect of the viper’s bite would be so certainly fatal that they might speak of him as, in effect, already dead—Beza.