John added Jesus' words that follow as a climactic appeal to his readers to believe on Jesus. This exhortation summarizes and restates some of the major points that John recorded Jesus teaching earlier. These themes include faith, Jesus as the One sent by the Father, light and darkness, judgment now and later, and eternal life. Jesus evidently gave it to the crowd as a final challenge. He probably delivered it during His week of teaching in the temple during the Passover season.
12:44-45 The fact that Jesus cried these words out shows their importance. Jesus again claimed to be God's agent and so closely connected with God that to believe on Jesus constituted believing on God. There is both a distinction between the Son and the Father in their subsistence and a unity between them in their essence (cf. ch. 5).
12:46 Jesus again claimed to have come to dispel darkness. He did this by revealing God (cf. 1:18).
12:47-48 Disobedience to Jesus' words may indicate the absence of saving faith (cf. 3:36). The same message that brings life to those who believe it will result in condemnation for those who reject it. The last day is the day unbelievers will stand before God in judgment, namely at the great white throne judgment (Rev. 20:11-15). God's purpose in the Incarnation was essentially positive, however. He wanted people to believe and experience salvation, not condemnation.
12:49-50 Jesus did not speak a message that He had devised but one that He had received from the Father (cf. Deut. 18:18-19). What God had commanded Him to say resulted in eternal life for those who believed it. Consequently Jesus was careful to convey this message exactly as He had received it.
This exhortation concludes and climaxes what John recorded of Jesus' public ministry.
