John Calvin Commentary Isaiah 16:9

"Therefore I will weep with the weeping of Jazer for the vine of Sibmah; I will water thee with my tears, O Heshbon, and Elealeh: for upon thy summer fruits and upon thy harvest the [battle] shout is fallen." — Isaiah 16:9 (ASV)

Therefore I will bewail. The Prophet here takes on the character of another person, as we have previously remarked, for in the name of the Moabites he laments and groans. It is undoubtedly true that believers always shudder at the judgments of God and cannot lay aside the feelings of human nature, so as not to feel pity for the destruction of the wicked.

Yet he does not describe his own feelings; his intention is to give additional weight to his instruction, so that no one may entertain a doubt regarding its fulfillment. He therefore represents, in the person of a Moabite, as on a stage, the mourning and grief that will be felt by all after that calamity, in order to offer to the Jews a confirmation of this promise, which otherwise might have been thought incredible.

Because on thy summer-fruits and on thy harvest a shouting shall break forth, or shall fall. This last clause of the verse is variously explained by commentators. נפל (naphal) signifies to fall, or to burst forth. Those who translate it, to burst forth, consider the word הידד (hedad), shouting, to refer to the enemies themselves; as if he had said, “The shouting of enemies bursts forth on your harvest;” so that there is an implied contrast between this shouting and the joy about which he will speak later.

Others explain it to mean that the shoutings will be laid; that is, “there shall be no more shouting, and no longer shall the glad and merry voices of the reapers be heard, cheering themselves after the harvest.” But I would rather refer it to the shouting of enemies; and on this point I follow a most faithful interpreter of this passage, the Prophet Jeremiah, who says that the spoiler bursts forth (Jeremiah 48:32), where Isaiah speaks of the shouting of the enemy; as if he had said, “When you make preparations for gathering in your harvest and your vintage, the enemies will rush in, and, instead of joy and cheerful song, their shouting shall be heard, which shall drive you far away.”