Isaiah 65:25

(See on Isa 11:6). and the lion shall eat straw like the bullock--(See on Isa 11:7). and dust--rather, "but dust," &c. The curse shall remain on the serpent [HORSLEY], (Gen 3:14; Mic 7:17). "To lick the dust" is figurative of the utter and perpetual degradation of Satan and his emissaries (Isa 49:23; Psa 72:9). Satan fell self-tempted; therefore no atonement was contrived for him, as there was for man, who fell by his temptation (Jde 1:6; Joh 8:44). From his peculiar connection with the earth and man, it has been conjectured that the exciting cause of his rebellion was God's declaration that human nature was to be raised into union with the Godhead; this was "the truth" concerning the person of the Son of God which "he abode not in"; it galled his pride that a lower race was to be raised to that which he had aspired to (Ti1 3:6). How exultingly he might say, when man fell through him, "God would raise manhood into union with Himself; I have brought it down below the beasts by sin!" At that very moment and spot he was told that the seed of the abhorred race, man, should bruise his head (Jo1 3:8). He was raised up for this, to show forth God's glory (Exo 9:16; Rom 9:17). In his unfallen state he may have been God's vicegerent over the earth and the animal kingdom before man: this will account for his assuming the form of a serpent (Gen 3:1).

— Jamieson-Fausset-Brown Commentary (public domain)