Complete Commentary on the Whole Bible, by Matthew Henry, at sacred-texts.com
(Jer 5:1-9) The Jews' profession of religion was hypocritical.
(Jer 5:10-18) The cruel proceedings of their enemies.
(Jer 5:19-31) Their apostacy and idolatry.
None could be found who behaved as upright and godly men. But the Lord saw the true character of the people through all their disguises. The poor were ignorant, and therefore they were wicked. What can be expected but works of darkness, from people that know nothing of God and religion? There are God's poor, who, notwithstanding poverty, know the way of the Lord, walk in it, and do their duty; but these were willingly ignorant, and their ignorance would not be their excuse. The rich were insolent and haughty, and the abuse of God's favours made their sin worse.
Multitudes are ruined by believing that God will not be so strict as his word says he will; by this artifice Satan undid mankind. Sinners are not willing to own any thing to be God's word, that tends to part them from, or to disquiet them in, their sins. Mocking and misusing the Lord's messengers, filled the measure of their iniquity. God can bring trouble upon us from places and causes very remote. He has mercy in store for his people, therefore will set bounds to this desolating judgment. Let us not overlook the "nevertheless," Jer 5:18. This is the Lord's covenant with Israel. He thereby proclaims his holiness, and his utter displeasure against sin while sparing the sinner, Psa 89:30-35.
Unhumbled hearts are ready to charge God with being unjust in their afflictions. But they may read their sin in their punishment. If men will inquire wherefore the Lord doeth hard things unto them, let them think of their sins. The restless waves obeyed the Divine decree, that they should not pass the sandy shores, which were as much a restraint as lofty mountains; but they burst all restraints of God's law, and were wholly gone into wickedness. Neither did they consider their interest. While the Lord, year after year, reserves to us the appointed weeks of harvest, men live on his bounty; yet they transgress against him. Sin deprives us of God's blessings; it makes the heaven as brass, and the earth as iron. Certainly the things of this world are not the best things; and we are not to think, that, because evil men prosper, God allows their practices. Though sentence against evil works is not executed speedily, it will be executed. Shall I not visit for these things? This speaks the certainty and the necessity of God's judgments. Let those who walk in bad ways consider that an end will come, and there will be bitterness in the latter end.