37 But although He had done so many signs before them, they did not believe in Him, 38 that the word of Isaiah the prophet might be fulfilled, which he spoke: “Lord, who has believed our report? And to whom has the arm of the Lord been revealed?” (John 12:37–38, NKJV)
The powerful arm of the Lord was revealed to Israel by the many signs (miracles) Jesus did before the people. His miracles were heaven’s testimony that He is the Christ, the Son of God (John 5:36; 20:30-31; Acts 2:22). Yet, despite His marvelous works, they did not believe in Him. Why not? John answers that question with another quote from Isaiah: “He has blinded their eyes and hardened their hearts, lest they should see with their eyes, lest they should understand with their hearts and turn, so that I should heal them” (John 12:40; Isaiah 6:9-10). It has been said there are none so blind as he who will not see. When we willfully harden our hearts against God and His Son, His testimony of truth will not penetrate it. We will remain lost in our unbelief. The strength of the Lord (His “arm”) has been revealed to the world through Jesus Christ. We must humble our hearts and open our eyes and ears to God’s powerful truth. By doing so, we can understand His will, turn back to God, and be healed of our sins.