“they have sinned against Yahweh.” Although in many places God goes into great detail about how the people have abandoned Him and the various sins they have committed, here in Zephaniah God justifies the Day of Yahweh and the vengeance associated with it by simply saying that people have “sinned against Yahweh.” That is all that needed to be said.
“their blood will be poured out like dust, and their bowels like dung.” The contrast of blood and bowels with dust and dung is sharp and striking. Blood and bowels are the very life of the person, and in that sense they are priceless. In contrast, dust and dung are worthless. In effect, God is making the point that people who arrogantly spurn God and live a life of sinning against Him are ultimately worthless. Although many versions say “flesh” instead of “bowels,” the Hebrew word is not “flesh,” but a word used for the bowels, intestines, entrails.
[For more on the destruction of the wicked in Gehenna, see commentary on Matt. 5:22. Also see Appendix 5, “Annihilation in the Lake of Fire”].