O my threshing - The words ‘to thresh,’ ‘to tread down,’ etc., are often used in the Scriptures to denote punishments inflicted on the enemies of God. An expression likes this occurs in Jeremiah 51:33, in describing the destruction of Babylon: ‘The daughter of Babylon is like a threshing floor; it is time to thresh her.’ In regard to the mode of threshing among the Hebrews, and the pertinency of this image to the destruction of the enemies of God, see the note at Isaiah 28:27. Lowth, together with many others, refers this to Babylon, and regards it as an address of God to Babylon in the midst of her punishment: ‘O thou, the object on which I shall exercise the severity of my discipline; that shall lie under my afflicting hand like grain spread out upon the floor to be threshed out and winnowed, to separate the chaff from the wheat.’ But the expression can be applied with more propriety to the Jews; and may be regarded as the language of “tenderness” addressed by God through the prophet to his people when they should be oppressed and broken down in Babylon: ‘O thou, my people, who hast been afflicted and crushed; who hast been under my chastening hand, and reduced to these calamities on account of your sins; hear what God has spoken respecting the destruction of Babylon, and your consequent certain deliverance.’ Thus it is the language of consolation; and is designed, like the prophecies in Isaiah 13; Isaiah 14, to comfort the Jews, when they should be in Babylon, with the certainty that they would be delivered. The language of “tenderness” in which the address is couched, as well as the connection, seems to demand this interpretation.
And the corn of my floor - Hebrew, ‘The son of my threshing floor’ - a Hebraism for grain that was on the floor to be threshed. The word ‘son’ is often used in this special manner among the Hebrews (see the note at Matthew 1:1).
That which I have heard ... - This shows the scope or design of the whole prophecy - to declare to the Jews the destruction that would come upon Babylon, and their own consequent deliverance. It was important that they should be “assured” of that deliverance, and hence, Isaiah “repeats” his predictions, and minutely states the manner in which their rescue would be accomplished.