Romans 11:10 - Ellicott's Commentary On The Whole Bible

Let their eyes be darkened. — In the Apostle’s sense, “Let them be spiritually blinded, incapable of discerning or receiving the truth, and let their backs be bowed with the yoke of spiritual thraldom!” The Hebrew is, “Let their eyes be darkened, that they see not, and make their loins continually to shake.” On which Perowne remarks: “The darkening of the eyes denotes weakness and perplexity, as the enlightening of the eyes denotes renewed vigour and strength. Similarly, the shaking of the loins is expressive of terror and dismay and feebleness.”