Luke 12:8-9
8 Also I say unto you, Whosoever shall confess me before men, him shall the Son of man also confess before the angels of God:
9 But he that denieth me before men shall be denied before the angels of God.
The Grace New Testament Commentary - Luke 12:8-9
12:8 To confess Jesus 'before men' means to acknowledge Him openly - especially in hostile contexts. The believer who does this can expect open praise and recognition at the future judgment of the believer. The confession here does not constitute a condition for eternal salvation. Further, it does not necessarily refer to a onetime public recognition of Jesus. Belief alone in Jesus results in eternal life and always happens secretly in the heart whether one openly confesses it or not (cf. John 12:42-43; Rom 10:10).
12:9 The believer who does not publicly confess Christ before men will not receive the commensurate recognition before God's angels. This denial does not affect the secure gift of eternal life which a believer possesses from the very instant in which he or she believes (see John 5:24-25). It does nevertheless represent loss of eternal rewards (2 Tim 2:11-13).
Charles Bing - Grace, Salvation, and Discipleship - Ashamed to Confess, Matthew 10:32-33; Mark 8:38 (cf. Luke 9:26; 12:8-9)
(Salvation) Interpretation: If a person does not confess Jesus publicly, he will be denied salvation, will prove he was never saved, or if saved, lose that salvation.
(Discipleship) Interpretation: If a Christian does not confess Jesus publicly or is ashamed of Him, that person will be denied the reward of Jesus' commendation before God the Father.
These passages have a similar theme: If someone denies the Lord Jesus or is ashamed of Him, he will be denied before God the Father and Jesus will be ashamed of him. These are tough words, so tough that many interpret them (Salvifically): Jesus will deny entrance into heaven and be ashamed in such a way that implies the person is unworthy of heaven.
Again, context is the key. In Matthew 10, Jesus is sending out His disciples with instructions and warnings about how they will be received and how they should not fear opposition. The warning of verses 32-33 about confessing (acknowledging) Jesus Christ could apply to those who hear the disciples' message, or it could apply to the disciples themselves, or it could be a principle that applies to both. Comparing Jesus' statement in Matthew with His similar statement in Luke 12:8-9, we find in both a common context about not fearing to speak to others about Christ. Though this could be a general principle, it certainly is addressed to the disciples first as both a warning and an encouragement.
In both Mark 8:38 and Luke 9:26, the statement is a warning without a corresponding encouragement. But this too is addressed to the disciples after Jesus tells them to deny themselves, take up their cross, and follow Him in order to "save" their lives. As we saw earlier, these are (Discipleship passages). Jesus explains that believers have choices and those choices have their respective consequences. One can identify with the world, lose his life, and earn Christ's shame, or one can identify with Christ. Though Mark and Luke's accounts do not mention a reward other than that one's life will be saved, Matthew's version goes on to speak of rewards in Matthew 10:41-42. The parallel account in Matthew 16:24-27 ends with a promise that when Jesus Christ returns, "He will reward each according to his works." Jesus' confessing or denying a confession and being ashamed are issues of rewards deserved by believers.
The negative "reward" (from misthos, which can also mean recompense, payment) for those who deny their identification with Christ or are ashamed of Him is that Jesus will not confess (acknowledge) them before the Father, or similarly, will be ashamed of them before the Father. Since this is in the context of (Discipleship), what does this mean? Since Jesus Christ's confession of someone before the Father is an acknowledgment of his or her faithfulness in identifying with Him, the negative of that is Jesus will withhold acknowledgment of that person. He will be ashamed in the sense of refusing to acknowledge him or her with a commendation before the Father.
That this is a consequence experienced only by Christians makes sense. It is no motivation to an unbeliever who rejects Christ not to be confessed before the Father or for Christ to be ashamed. In light of his decision to have nothing to do with Jesus Christ, what would he or she care? But to those who have a relationship with Jesus Christ, to earn a word of approval or disapproval, or to make Christ ashamed would have a great motivating impact. The believer knows the love of God and the sacrifice Jesus has made for him by dying on the cross. Disapproval and shame assume a degree of relationship. For example, imagine a boy misbehaving in a shopping mall. While others walk by nonplussed, one man's face is flushed with embarrassment and his head is lowered in shame. That is the boy's father. The son disappointed his father's expectations.
Our Savior's approval or disapproval of our conduct and choices should be a motivation to us who are children of a Heavenly Father. In the end, it is the only approval that really matters. Publicly identifying with Jesus Christ may or may not win approval from others in this world, but either way, the effect is temporary. God's approval is eternal.