John 12:11

Because that by reason of him many of the Jews went away, and believed on Jesus.

Because of Lazarus, whom Jesus had raised from the dead, many of the Jews left the influence and hold of the chief priests and rulers and believed on Jesus.
This took place when Jesus rested at Bethany at the supper in His honor, with Lazarus raised from the dead beside Him, and crowds came to see Jesus and Lazarus and then spread the report at Jerusalem.
Lazarus was a living witness whose presence and testimony that Jesus is the Son of God and the Messiah gave convincing evidence of Christ's power and drew people to faith.
His witness could not be denied, for he had lain dead four days with his body begun to decay until called to life by a word from Jesus, making his resurrection the crowning miracle of Christ's life and the last test to the nation.
Though the priests and rulers could not refute the miracle, they feared losing their hold on the people and plotted in hasty council to put Lazarus to death as well as Jesus, and those who rejected such evidence hardened their hearts against truth.

Context and Cause

Six days before the Passover, on the way from Jericho to Jerusalem for the feast, Jesus stopped in Bethany for rest and refreshment. A supper was made there in His honor by Simon of Bethany, whom He had healed of leprosy. At the table Jesus sat with Simon, cured of a loathsome disease, on one side and Lazarus, raised from the dead, on the other, while Martha served and Mary listened earnestly to every word He spoke.

The reason many of the Jews believed on Jesus was Lazarus, whom He had raised from the dead. His presence and the fact of his raising led them to faith, and his return to life drew them to turn away from the authorities and believe. His raising provided powerful evidence of divinity, and he bore witness to Jesus as he had been raised.

Believing on Jesus meant going away from the Jewish authorities, leaving their influence and hold. It was a departure from the chief priests, priests, and rulers, turning from them to Christ. His living testimony drew people to faith and weakened the rulers' hold on them.

News of the astonishing miracle drew many people to Bethany to see Jesus and Lazarus. Some came out of curiosity to see Lazarus, and others because they cared for Jesus and wanted to see and hear Him. His continued life was a public testimony to Jesus' power, drawing people to see him and strengthening their belief. Those who returned to Jerusalem brought reports that increased the excitement of the multitude, so that all were anxious to see and hear Jesus whose fame as a prophet had spread. Public attention was entirely fixed on Jesus and His works, with people asking who He was, where He came from, whether Lazarus who had been raised from the dead would accompany Him to Jerusalem, and whether He would be crowned king at the Passover feast.

Witness and Rejection

Lazarus stood as a living witness whose very presence drew people to faith, and his clear testimony to Christ's power gave convincing evidence that could not be set aside. He declared that Jesus is the Son of God and the Messiah, the great Restorer, and his witness bore directly to the divinity of Jesus. Because he had been raised from the dead, many left the influence of the leaders and believed, and public sympathy was turned toward Jesus. His testimony weakened the rulers' hold on the people, and though they tried to suppress the evidence, it continued to convince many that Jesus was the Messiah.

His testimony was undeniable because he had lain four days in the grave with his body begun to decay before being called to life and health by a word from Jesus spoken for the benefit of humanity. His visible life after such death gave clear and convincing proof of divine power at work through Christ. His resurrection was the crowning miracle of Christ's life and the last test given to the Jewish nation.

The priests and rulers could neither refute nor deny the miracle, yet they refused to accept it. They feared that if Lazarus remained alive as a witness, a reaction would sooner or later be created against them. They saw they were losing their hold on the minds of the people, and they feared that if the people lost confidence in their rulers the national power would be destroyed. They feared it would bring disaster upon them to have sacrificed One who could perform such a miracle.

Because his raising had so greatly turned the sympathies of the people toward Jesus and caused many to believe, the priests and Pharisees in hasty council decided Lazarus must die as well as Jesus. The growing crowds that came to see Lazarus and hear Jesus made them fear that all would believe, so they plotted to kill both. An open seizure of Jesus was judged too dangerous, so they planned craft and secret arrest and a quiet mock trial. They trusted the fickle tide of public opinion would set in their favor once He was known to be condemned to death.

Though no charge could be brought against Lazarus, those who rejected this undeniable evidence plotted to kill him to stop more from believing. Others who saw the same evidence rejected it and hardened their hearts. Such unbelief hardens the heart, resists truth, and rejects the impressions of the Holy Spirit.