Charles Ellicott Commentary 1 Samuel 11:2

"And Nahash the Ammonite said unto them, On this condition will I make it with you, that all your right eyes be put out; and I will lay it for a reproach upon all Israel." — 1 Samuel 11:2 (ASV)

On this condition. —The horrible cruelty of this scornful proposal gives us an insight into the barbarous customs of this imperfectly civilized age. Indeed, many of the crimes we read of in these books—crimes which, to modern ears, justly sound shocking and scarcely credible—can be attributed to the fact that civilization and its humanizing influences had made little progress yet among the nations of the world.

The purpose of Nahash’s cruelty was to incapacitate the inhabitants of Jabesh from ever again assisting his enemies in war; they would from then on be blinded in the right eye, while the left eye would be concealed by the shield which fighting-men customarily held before them.