Verse 19: Thou believest that there is one God; thou doest well: (Matt. 8:29; Mark 1:24; 5:7; Luke 4:34; Acts 16:17; 19:15) the devils also believe, and tremble.
[Thou believest that there is one God] That is, that there is a God, and that He is one (Grotius, thus Estius), not many (Estius, Piscator), Deuteronomy 4:35, 39; 6:4 (Grotius). This he takes as an example (Estius, Grotius), because it is first among things to be believed (Grotius, similarly Estius), in the Apostolic Creed (Estius); and by which the Jews were distinguished from Atheists, and from the Greeks (Grotius), or Pagans (Estius), upon which also the mission and authority of Christ depends, and all faith in Christ. For Christ has authority from that one and true God, John 14:1; 17:3 (Grotius). Now, concerning the other articles of the faith, the judgment is the same (Estius).
Thou believest that there is one God; thou givest thy assent to this truth, that there is one God. This may likewise imply other articles of the creed, to which the like assent may be given.
[Thou doest well] That is to say, This is good (Grotius), because what you believe is true (Piscator), and this act is good in its kind (Estius). But this is not sufficient for salvation (Grotius), as you falsely suppose (Piscator).
[The demons also, etc., καὶ τὰ δαιμόνια—φρίσσουσι] That knowledge is not so sufficient that it is common to thee with the depraved Spirits (Grotius, similarly James Cappel). But also the demons (ערים, both to the Rabbis and to the Seventy in Isaiah 13:21 [Grotius], or, evil spirits [Grotius], understanding this [Piscator, thus Beza], or, the same [Grotius], namely, that God is one [Beza], and so also the other articles of our creed, as it appears from Matthew 8; Mark 5; Acts 16; 19 [Estius]) believe (by Faith, either supernatural, as Durandus, Lombard, and Salmasius think; and demonstrable, as Lapide, Just., etc.; or natural [Tirinus], not by a faith infused divinely, but from the subtlety of nature; convinced, not voluntarily, but by compulsion, and by the evidence of things, and by true miracles [Estius]: which faith, nevertheless, profits them nothing except unto greater torment [Tirinus]), but they nevertheless shudder (Piscator, similarly Beza), or, and they tremble (Grotius out of the Syriac and Arabic, thus the Vulgate). By Metonymy that word signifies enormous fear, and is translated in the Glossa, horresco, to dread. Thence φρικτῶς/horribly, in Wisdom of Solomon 6:5; and φρικτὸν/horrible, שַׁעֲרוּרִיָּה, in Jeremiah 5:30; 18:13; 23:14; and φρικῶδες, a thing that causes horror, in Hosea 6:10. The sense: Not only do they have no hope of salvation, but also on account of their depravity they expect more grievous torments with fear. See Matthew 8:29; 2 Peter 2:4; Jude 6; Revelation 20:10 (Grotius). They fear and flee from Him (Grotius, Estius), whom they expect as a most resolute and severe judge (Estius), the avenger of their wickedness, 2 Peter 2:4; Jude 6 (Grotius), whose majesty, power, severity, they not only believe in, but also actually experience and feel (Menochius). Thus also you ought to fear this same God if you imitate the deeds of the Devil (Grotius).
Thou doest well; either this kind of faith hath its goodness, though it be not saving; or ironically, q.d. A great matter thou dost, when thou goest almost as high as the devils. The devils also believe; yield the like assent to the same truth. And tremble: the word signifies extreme fear and horror, viz. such as the thoughts of their Judge strike into them. This shows the faith the apostle speaks of in this place, not to be the faith of God’s elect, which begets in believers a holy confidence in God, and frees them from slavish fears; whereas the faith here spoken of, if it have any effect upon men, it is but to fill them with horror.
 Greek: σὺ πιστεύεις ὅτι ὁ Θεὸς εἷς ἐστί· καλῶς ποιεῖς· καὶ τὰ δαιμόνια πιστεύουσι, καὶ φρίσσουσι.
 Isaiah 13:21: “But wild beasts of the desert shall lie there; and their houses shall be full of doleful creatures; and owls shall dwell there, and satyrs (וּשְׂעִירִים; καὶ δαιμόνια, in the Septuagint) shall dance there.”
 That is, the demons also believe this.
 Durandus of Saint-Pourçain (c. 1275-c. 1332) was a French Dominican philosopher and theologian. He lectured and wrote commentaries on Lombard’s Sentences. In some matters, he differed from the great Dominican theologian, Thomas Aquinas, and became known as the Doctor Resolutissimus for his firm adherence to his novel positions.
 Peter Lombard (c. 1096-c. 1164), although of relatively humble birth, became a renowned theologian in Paris. His Four Books of Sentences served as a standard theological text at medieval universities.
 Cornelius à Lapide (1567-1637) was a Flemish Jesuit scholar. His talents were employed in the professorship of Hebrew at Louvain, then at Rome. He wrote commentaries covering the entire Roman Catholic canon, excepting only Job and the Psalms, developing the four-fold sense of Scripture, while emphasizing the literal. His knowledge of Hebrew, Greek, and the commentators that preceded him is remarkable.
 Wisdom of Solomon 6:5: “Horribly (φρικτῶς) and speedily shall he come upon you: for a sharp judgment shall be to them that be in high places.”
 Jeremiah 5:30: “A wonderful and horrible (וְשַׁעֲרוּרָה; καὶ φρικτὰ, in the Septuagint) thing is committed in the land…”
 Jeremiah 18:13: “Therefore thus saith the Lord; Ask ye now among the heathen, who hath heard such things: the virgin of Israel hath done a very horrible (שַׁעֲרֻרִת; φρικτά, in the Septuagint) thing.”
 Jeremiah 23:14a: “I have seen also in the prophets of Jerusalem an horrible thing (שַׁעֲרוּרָה; φρικτά, in the Septuagint): they commit adultery, and walk in lies…”
 Hosea 6:10: “I have seen an horrible thing (שַׁעֲרִירִיָּה; φρικώδη, in the Septuagint) in the house of Israel: there is the whoredom of Ephraim, Israel is defiled.”