Mystery of Israel's Blindness

Spiritual blindness is a serious issue. If not faced, it can lead to death: that is, an eternal separation from God in the Lake of Fire. In the case of our passage, it is a judicial punishment brought upon a people for living in disobedient unbelief.
Though our passage references Israel’s hardening, our text also warns the Gentile nations of this danger in Romans 11:21-22, “Be not highminded, but fear: For if God spared not the natural branches (which is the nation of Israel), take heed lest he also spare not thee (the Gentile). Behold therefore the goodness and severity of God: on them which fell, severity; but toward thee, goodness, if thou continue in his goodness: otherwise thou also shalt be cut off.”