"Afterward He appeared unto the eleven as they sat at meat, and upbraided them with their unbelief and hardness of heart, because they believed not them which had seen Him after He was risen" (Mark 16:14).
Apparently many people--even Christians--are afflicted with "spiritual cardiosclerosis" (hardening of the heart), for there are some forty references in the Bible to this malady. The first was in reference to Egypt's unbelieving Pharaoh. Concerning him, God told Moses: "I will harden his heart, that he shall not let the people go" (Exodus 4:21).
But when the children of Israel did escape Pharaoh's persecutions, they also contracted this debilitating attitude: "Harden not your heart, as in the provocation, and as in the day of temptation in the wilderness: When your fathers tempted me, proved me, and saw my work" (Psalm 95:8-9).
Even the very disciples of the Lord Jesus Christ were rebuked by Him for their hardness of heart. In spite of the Old Testament prophecies, and in spite of His own repeated promise that He would rise from the dead, the disciples forsook Him and fled into hiding when He was arrested. Some were even skeptical about the first reports of His resurrection until they saw Him for themselves. His rebuke (see our text) essentially equated their unbelief with "hardness of heart" (Greek, sklerokardia).
If this heart of hardness and unbelief could attack the eleven disciples, it could surely happen to us, if we allow it. "Take heed, brethren, lest there be in any of you an evil heart of unbelief. . . . But exhort one another daily . . . lest any of you be hardened through the deceitfulness of sin. . . . To day if ye will hear His voice, harden not your hearts" (Hebrews 3:12-13,15). Instead, we should heed Christ's first great commandment: "Thou shalt love the Lord thy God with all thy heart" (Matthew 22:37). HMM