C. F. Keil and Franz Delitzsch on Jeremiah 5:3

Jer 5:3

The eye of the Lord is directed towards faithfulness, which is not to be found in Jerusalem (Jer 5:1), ל showing the direction toward person or thing, as in Psa 33:18, where ל alternates with אל. Hitz. is wrong in translating: are not thine eyes faithful, i.e., directed according to faithfulness; a sense quite unsuitable here, since the matter in hand is not the character or direction of the eye of God, but that on which God looks. But because God desired sincerity, and there was none in the people of Jerusalem, He has smitten them, chastised them, but they felt no pain (חלוּ from חלה, the tone being drawn back by reason of the  '); the chastisement made no impression. Thou consumedst them, exterminatedst them, i.e., "Thou hast utterly exterminated multitudes and swarms of them" (Hitz.), but they refused to receive correction; cf. Jer 2:30. They made their face harder than rock, i.e., hardened themselves by obstinately setting the divine chastisements at naught; cf. Eze 3:7-8.