12:37-38 The majority of the Jews did not believe on Jesus despite the many miracles that He performed that indicated His messiahship (cf. 1:11). John again attributed Israel's unbelief to God's will, though he balanced that again with the Jew's human responsibility in verse 43. He viewed Isaiah 53:1 as predicting Israel's rejection of her Messiah. The verse originally referred to the Gentiles' rejection of Israel, the servant of the Lord. However in another sense it predicted Israel's rejection of the Servant of the Lord whom He would send. The report or message that the people had rejected was Jesus' teaching, and the evidence of the Lord's arm or power was Jesus' miracles.
"John 12 records the second major crisis in the ministry of our Lord as seen by John the apostle. The first occurred when many of His disciples would no longer walk with Him (John 6:66), even though He is the way' (John 14:6). In this chapter, John tells us that many would not believe in Him (John 12:37ff), even though He is the truth.' The third crisis will come in John 19: even though he is the life,' the leaders crucified Him."424
12:39 John again affirmed that most of the Jews did not believe on Jesus because they could not. God had judicially hardened their hearts because they had refused to believe Him previously (cf. Exod. 9:12; cf. 2 Thess. 2:8-12).
12:40 Isaiah 6:10 is the prophecy that predicted this hardening (cf. Acts 28:26-27). Originally God had told Isaiah that the people to whom he ministered would not welcome his ministry because God would harden their hearts. Now John explained that this verse also revealed the reason for the Jews' rejection of Jesus' ministry. Prophecy not only described Israel's unbelief (v. 38), but it also explained it.
The apostle Paul gave the definitive answer to the problem of God's fairness that His predestination poses in Romans 9-11.
12:41 In the vision that Isaiah recorded in Isaiah 6, the prophet wrote that he saw God's glory (Isa. 6:3). Now John wrote that Isaiah saw Jesus' glory and spoke of Jesus. Obviously John regarded Jesus as God (cf. 1:18; 10:30; 20:28; Col. 2:9). Isaiah had spoken of Jesus in that he had revealed many messianic prophecies. Earlier Jesus had claimed that Moses had written about Him (5:46).
These quotations justify interpreting the Old Testament servant of the Lord passages as referring to the Messiah. Today there is a debate within Judaism and liberal Christianity about whether these passages refer to a personal Messiah or only to Israel.
12:42-43 Even though most of the Jews rejected Jesus, some believed on Him (cf. 1:10-13). Even some of the rulers did, though the content of their faith doubtless varied. Nicodemus and Joseph of Arimathea seem to have been such people (cf. 7:50-52; 19:38-39). Most of them did not admit that they believed in Him, however, because of fear of exclusion from synagogue worship (cf. 9:22).
Public confession of faith in Jesus is the normal expression of belief in Him (Rom. 10:9-10). However public confession is not a condition for salvation. Obviously mutes and other people can believe but for one reason or another may not be able to confess their faith publicly with their mouths.