Isaiah 65:8

In the figure, the grape-cluster represents the nation as a whole, including many unworthy members, the "new wine" (iîrôsh, "must") is the spiritual kernel of the nation, here called "my servants"; and the truth taught is that for the sake of the latter "the whole" shall not be annihilated in the judgement that is to come. It is an application to new circumstances of Isaiah's doctrine of the Remnant (ch. Isaiah 6:13).

The words Destroy it not, for a blessingis in ithave been thought, from their rhythm, to be the first line of one of the vintage songs often referred to in Scripture (cf. Judges 9:27; Isaiah 16:10; Jeremiah 25:30; Jeremiah 48:33, &c.). It has further been conjectured that the words "Destroy not" ("al tashḥçth) in the headings of four psalms (57, 58, 59, 75) refer to this song, naming its melody as the tune to which these Psalms were to be sung (W. R. Smith, O. T. in Jewish Church2, p. 209).

thatI may not &c. (so as) not to destroy the whole.