Joel 1:6
For a nation is come up upon my land, strong, and without number, whose teeth are the teeth of a lion, and he hath the cheek teeth of a great lion. For a nation is come up upon my land, strong, and without number, whose teeth are the teeth of a lion, and he hath the cheek teeth of a great lion.
The devouring nation foretells the moral and spiritual condition of the world just before the second coming. That final period is characterized by abounding iniquity springing from widespread transgression of God's law. In breaking that law men break the everlasting covenant, and this covenant-breaking accounts for the desolation described.