Grain must be ground to make bread; so one does not go on threshing it forever. The wheels of a threshing cart may be rolled over it, but one does not use horses to grind grain.
NIV
Does one crush bread grain? No, he does not thresh it continuously. But when he has driven his cartwheel and his horses over it, he scatters it [tossing it up to the wind] without having crushed it.
AMP
Bread corn is bruised; because he will not ever be threshing it, nor break it with the wheel of his cart, nor bruise it with his horsemen.
KJV