He hath shewed strength with his arm; he hath scattered the proud in the imagination of their hearts. He hath showed strength - Or, He hath gained the victory, εποιησε κρατος. The word κρατος is used for victory, by Homer, Hesiod, Sophocles, Euripides, and others.
With his arm - Grotius has well observed, that God's efficacy is represented by his finger, his great power by his hand, and his omnipotence by his arm. The plague of lice was the finger of God, Exodus 7:18. The plagues in general were wrought by his hand, Exodus 3:20, And the destruction of Pharaoh's host in the Red Sea, which was effected by the omnipotence of God, is called the act of his arm, Exodus 15:16.
He hath scattered - Διεσκορπισεν, hath scattered abroad; as a whirlwind scatters dust and chaff.
The proud - Or haughty, ὑπερηφανους; from ὑπερ above, and φαινω I show - the haughty men, who wish to be noticed in preference to all others, and feel sovereign contempt for all but themselves. These God scatters abroad - instead of being in his sight, as in their own, the most excellent of the earth, he treats them as straw, stubble, chaff, and dust.
In the imagination of their hearts - While they are forming their insolent, proud, and oppressive projects - laying their plans, and imagining that accomplishment and success are waiting at their right hand, the whirlwind of God's displeasure blows, and they and their machinations are dissipated together.