John Gill Commentary Jeremiah 5:27

"As a cage is full of birds, so are their houses full of deceit: therefore they are become great, and waxed rich." — Jeremiah 5:27 (ASV)

As a cage is full of birds
Jarchi and Kimchi understand it of a place in which fowls are brought up and fattened, what we call a "pen"; and, so the Targum renders it, a house or place of fattening. The word is rendered a "basket" in (Amos 8:1Amos 8:2) and may here design one in which birds taken in snares, or by hawking, were put. The Septuagint version, and those that follow it, render it, "a snare": which agrees with what goes before. It seems to intend a decoy, in which many birds are put to allure others; and, what with them, and those that are drawn in by them, it becomes very full; and this sense of the comparison is favoured by the rendition or application, which follows:

so are their houses full of deceit ;
of mammon, gathered by deceit, as Kimchi interprets it; ungodly mammon; riches got in a fraudulent way, by cozening and cheating, tricking and overreaching:

therefore they are become great ;
in worldly things, and in the esteem of men, and in their own opinion, though of no account with God:

and grown rich ;
not with the true riches, the riches of grace, the unsearchable riches of Christ, his durable riches and righteousness; nor indeed with the riches of the world, honestly and lawfully gotten; but with unrighteous mammon.