Joel 3:14

“Multitudes, multitudes in the valley of decision, etc.] The same with the valley of Jehoshaphat before mentioned; which shows that not any valley of that name is intended, but a certain place so called from the judgments of God in it; and here named “the valley of decision”, because here their judgment will be determined, as Kimchi and Jarchi; and at this time the controversy between God, and his people’s enemies, will be decided, and at an end: or “the valley of concision”, as the Vulgate Latin version; because in this place, and at this time, the nations gathered together in it will be cut to pieces: or, as others, “the valley of threshing” F87 ; because, as, in Jehoshaphat’s time, the…”

“The prophet in vision seeing the immense array of nations congregating, exclaims, "Multitudes, multitudes!" a Hebraism for immense multitudes. valley of decision--that is, the valley in which they are to meet their "determined doom." The same as "the valley of Jehoshaphat," that is, "the valley of judgment" (see on Joe 3:2). Compare Joe 3:12, "there will I sit to judge," which confirms English Version rather than Margin, "threshing." The repetition of "valley of decision" heightens the effect and pronounces the awful certainty of their doom.”

“The prophet continues, as in amazement at the great throng assembling upon one another, “multitudes, multitudes, in the valley of decision,” as though, whichever way he looked, there were yet more of these “tumultuous masses,” so that there was nothing beside them. It was one living, surging, boiling, sea: throngs upon throngs, mere throngs! . The word rendered “multitudes” suggests, besides, the thought of the hum and din of these masses thronging onward, blindly, to their own destruction. They all “tumultuously rage together, and imagine a vain thing, against the Lord and against His Christ” Psalms 2:1-2; but the place where they are gathered, (although they know it not,) is the “valley of…”

“In the valley of decision - Where God having gathered them, decided their quarrels, and by the conqueror punish the conquered for their sins against God and his people. The day - The day of vengeance. Joel 3:16”

“3:14 Thousands upon thousands (literally roaring, roaring; or crowds, crowds): The repetition of the Hebrew word captures the chaotic noise made by an immense crowd. • valley of decision: The name of the valley is changed (cp. 3:2-3, 12) because now the Lord’s judgment had been decided.”

“multitudes: Joe 3:2; Isa 34:2-8, Isa 63:1-7; Ezek. 38:8-23, Eze 39:8-20; Rev 16:14-16, Rev 19:19-21 decision: or, concision, Phi 3:2, or, threshing for: Joe 2:1; Psa 37:13; Pe2 3:7 Joel 3:15”