Like fluttering birds pushed out of the nest, so are the daughters of Moab at the fords of the Arnon:
2. It shall be as a bird let loose. {Bogus footnote} The Prophet now shows what he meant by the former mockery, that the Moabites ought not at that time to think of sending sacrifices, because they will not be able to provide for their safety in any other way than by leaving their native country.
God has made it to appear that he delights not in the ruin of sinners by telling them what they may do to prevent the ruin; so he does here to Moab. I. He advises them to be just to the house of David, and to pay the tribute they had formerly covenanted to pay to the kings of his line (Isa 16:1): Send you...
Commenting on Isaiah 16:1-5
For it shall be,.... Or, "otherwise it shall be" (z); if ye do not pay this tribute: that as a wandering bird cast out of the nest: or, "as a wandering bird, the nest sent out": that is, as a bird that has forsaken its nest, and wanders about, and its young ones are turned out of the nest, scarcely fledged, and unable to shift...