I will spend mine arrows upon them - The judgments of God in general are termed the arrows of God, Job 6:4; Psalm 38:2, Psalm 38:3; Psalm 91:5; see also Ezekiel 5:16; Jeremiah 50:14; 2-Samuel 22:14, 2-Samuel 22:15. In this and the following verses, to the 28th inclusive, (Deuteronomy 32:23-28), God threatens this people with every species of calamity that could possibly fall upon man. How strange it is that, having this law continually in their hands, they should not discern those threatened judgments, and cleave to the Lord that they might be averted!
It was customary among the heathens to represent any judgment from their gods under the notion of arrows, especially a pestilence; and one of their greatest deities, Apollo, is ever represented as bearing a bow and quiver full of deadly arrows; so Homer, Il. i., ver. 43, where he represents him, in answer to the prayer of his priest Chryses, coming to smite the Greeks with the pestilence: -
Ὡς εφατ' ευχομενος· του δ' εκλυε Φοιβος Απολλων·
Βη δε κατ' Ουλυμποιο καρηνων χωομενος κηρ,
Τοξ' ωμοισιν εχων αμφηρεφεα τε φαρετρην. -
Ἑζετ' επειτ' απανευθε νεων· μετα δ' ιον ἑηκε·
Δεινη δε κλαγγη γενετ' αργυρεοιο βιοιο. κ. τ. λ.
"Thus Chryses pray'd; the favoring power attends,
And from Olympus' lofty tops descends.
Bent was his bow the Grecian hearts to wound;
Fierce as he moved, his silver shafts resound; -
The fleet in view, he twang'd his deadly' bow,
And hissing fly the feather'd fates below.
On mules and dogs the infection first began;
And last the vengeful arrows fix'd in man."
How frequently the same figure is employed in the sacred writings, every careful reader knows; and quotations need not be multiplied.

I will heap mischief upon them,.... One calamity upon another, which are after particularly mentioned:
I will spewed mine arrows upon them; God is here represented as an enemy to the Jews, as having bent his bow against them like an enemy, Lamentations 2:4; and as having a quiver, and that full of arrows, and as determined to draw out and spend everyone of them, in taking vengeance upon them; which arrows are his four sore judgments mentioned Ezekiel 14:21; and expressed in Deuteronomy 32:24.

I will spend mine arrows upon them--War, famine, pestilence (Psalm 77:17) are called in Scripture the arrows of the Almighty.

"I will heap up evils upon them, use up My arrows against them." The evils threatened against the despisers of the Lord and His commandments would be poured out in great abundance by the Lord upon the foolish generation. ספה, to add one upon the other (vid., Numbers 32:14); hence in Hiphil to heap up, sweep together. These evils are represented in the second clause of the verse as arrows, which the Lord as a warrior would shoot away at his foes (as in Deuteronomy 32:42; cf. Psalm 38:3; Psalm 91:6; Job 6:4). כּלּה, to bring to an end, to use up to the very last.

Spend mine arrows - Even empty my quiver, and send upon them all my plagues, which, like arrows shot by a skilful and strong hand, shall speedily reach and certainly hit and mortally wound them.