When they couch in their dens - For the purpose of springing upon their prey.
And abide in the covert to lie in wait? - The usual posture of the lion when he seeks his prey. He places himself in some unobserved position in a dense thicket, or crouches upon the ground so as not to be seen, and then springs suddenly upon his victim. The common method of the lion in taking his prey is to spring or throw himself upon it from the place of his ambush, with one vast bound and to inflict the mortal blow with one stroke of his paw. If he misses his aim, however, he seldom attempts another spring at the same object, but deliberately returns to the thicket in which he lay in concealment. See the habits of the lion illustrated in the Edinburgh Encyclopedia, "Mazology."

When they couch in their dens - Before they are capable of trusting themselves abroad.
Abide in the covert - Before they are able to hunt down the prey by running. It is a fact that the young lions, before they have acquired sufficient strength and swiftness, lie under cover, in order to surprise those animals which they have not fleetness enough to overtake in the forest; and from this circumstance the כפירים kephirim, "young lions, or lions' whelps," have their name: the root is כפר caphar, to cover or hide. See the note on Job 4:11, where six different names are given to the lion, all expressing some distinct quality or state.

When they couch in their dens, and abide in the covert to lie in wait? Which some understand of old lions, who, for want of strength, lie couchant in their dens, or in some covert place, waiting for any prey that passes by, to seize upon it. But the same pasture and places are used by younger lions, as well as old ones; who are emblems of wicked men, cruel persecutors, and bloodthirsty tyrants, who fill their palaces and kingdoms with murder and rapine; see Psalm 10:8, Nahum 2:11.

lie in wait?--for their prey (Psalm 10:9).