Paul declares: "If we deny Him, He also will deny us" (v. 12). Paul is simply echoing the statement of Jesus in Matthew 10:32-33 - 'Everyone therefore who shall confess Me before men, I will also confess him before My Father who is in heaven. But whoever shall deny Me before men, I will also deny him before My Father who is in heaven.' Make no mistake about it: to deny Jesus, to repudiate him, to declare that he is not the Son of God incarnate and that he did not die for sinners and that he did not rise from the dead and that he is not the only way to the Father results in eternal death. Anyone and everyone who denies the Son shall himself/herself be denied.
Note: The preacher's 'we' is used frequently in our preaching and writing today. If I am speaking to an audience in which I suspect are both Christians and non-Christians (and most likely all audiences contain both), I would say something like this: 'People, hear me well. If we believe in Jesus we will be saved. However, if we turn our back on him and the offer of life that is based on his atoning sacrifice we will be forever lost.' In using such terms ('if' and 'we') I'm not suggesting that I don't already believe in Jesus nor that I might deny him in the future. It is an appeal and a warning to anyone and everyone in which fundamental truths and their consequences are stated.
Be it also noted that Paul does not have in mind the kind of 'denial' into which Peter fell. In Peter's case, the 'denial' was momentary and was followed by great remorse and repentance. The 'denial' Paul has in view in 2 Timothy is both persistent and final, an utter and absolute repudiation of Jesus. Says Knight:
"The statement in the saying that we are now considering does not mean that Christ is not faithful to his promise to us, nor does it mean that our fall into a denial even as grave as Peter's is unforgivable or that it from that time henceforth forever and ever seals our doom. The denial in view in the saying which calls forth Christ's denial is not like that of Peter's who later sought forgiveness but rather is a situation of hardness and permanence" (Sayings, 126).