Isaiah 1:20

Ye shall be devoured with the sword "Ye shall be food for the sword" - The Septuagint and Vulgate read תאכלכם tochalchem, "the sword shall devour you;" which is of much more easy construction than the present reading of the text.

The Chaldee seems to read בחרב אויב תאכלו bechereb oyeb teachelu, "ye shall be consumed by the sword of the enemy." The Syriac also reads בחרב beehereb and renders the verb passively. And the rhythmus seems to require this addition. - Dr. Jubb.

But if ye refuse, ye shall be devoured with the sword - Your enemies shall come in, and lay waste the land. This prediction was fulfilled, in consequence of their continuing to rebel, when the land was desolated by Nebuchadnezzar, and the nation was carried captive to Babylon. It illustrates a general principle of the divine government, that if people persevere in rebelling against God, they shall be destroyed. The word devour is applied to the sword, as if it were insatiable for destruction. Whatever destroys may be figuratively said to devour; see the notes at Isaiah 34:5-6; compare Isaiah 5:24; Lamentations 2:3; Ezekiel 15:4; Joel 2:3; Revelation 11:5 - where fire is said to devour.

The mouth of the Lord - Yahweh Himself. This had been spoken by the mouth of the Lord, and recorded, Leviticus 26:33 :

And I will scatter you among the heathen,

And will draw out a sword after you;

And your land shall be desolate

And your cities waste.

On these points God proposed to reason; or rather, perhaps, these principles are regarded as reasonable, or as commending themselves to men. They are the great principles of the divine administration, that if people obey God they shall prosper; if not, they shall be punished. They commend themselves to people as just and true; and they are seen and illustrated every where.