John Calvin on Obadiah 1:6

He confirms the former sentence, — that the Idumeans in vain trusted that their riches would be safe, because they had hidden and deep recesses. Even when a country is plundered by enemies, the conquerors dare not to come to places of danger; when there are narrow passes, they avoid them, for they think that there is there some evil design. Hence conquerors, fearing hidden places, plunder only those which are open, and always consider well whether their advance is safe: but Idumea, as we have said, had hidden recesses, for its rocks were almost inaccessible, and there were many conveniences there for hiding and concealing its riches. But the Prophet says, that all this would be useless: and that he might more effectually rouse them, he speaks with astonishment, as of something incredible. How have been sought the things of Esau, and thoroughly searched his hidden places! Who could have thought this? for they might have concealed their treasures in rocks and caverns, and thence repelled their enemies. But in vain would be all their attempts: how could this possibly be? Here then he awakens the minds of men, that they might acknowledge the judgment of God; and at the same time he laughs to scorn the vain confidence with which the Idumeans were inflated; and besides, he strengthens the minds of the godly, that they might not doubt but that God would perform what he declares, for he can indeed penetrate even to the lowest deep.

In short, the Prophet intimates that the faithful did not act wisely, if they measured God’s vengeance, which was impending on the Idumeans, by their own understanding or by what usually happens; for the Lord would make a thorough search, so that no hiding-places would escape his sight; and then all their treasures would be exposed as a prey to their enemies. We hence learn, that as men in vain seek hiding places for themselves that they may be safe from dangers; so in vain they conceal their riches; for the hand of God can penetrate beyond the sea, land, heaven, and the lowest deep. Nothing then remains for us but ever to offer ourselves and all our things to God. If he protects us under his wings, we shall be safe in the midst of innumerable dangers; but if we think that subterfuges will be of any avail to us, we deceive ourselves. The Prophet now adds —

Obadiah 7-8

7. All the men of thy confederacy have brought thee even to the border: the men that were at peace with thee have deceived thee, and prevailed against thee; they that eat thy bread have laid a wound under thee: there is none understanding in him.

7. Usque ad terminum expulerunt te omnes viri foederis tui; deceperunt te, praevaluerunt tibi, viri pacifici tui (viri pacis tuae;) viri panis tui posuerunt vulnus sub te: nulla est intelligentia in eo.

8. Shall I not in that day, saith the Lord, even destroy the wise men out of Edom, and understanding out of the mount of Esau?

8. Annon in die illa, dicit Jehova, perdam sapientes ex Edom? Et intelligentiam e monte Esau? (hoc est, e monte Seir.)