Peter cautions that some of the things the apostle Paul writes are hard to understand, as though some people do not truly understand Paul's lyrics and thus end up with wrong impressions of his compositions. Knowing a couple of lines from a piece of music is not the same as grasping the totality. Yet, nominal Christianity gives an embarrassing performance before God because it latches onto some memorable lines from Paul and believes it knows the whole song.
The terms Peter uses provide clues about what is on his mind. When we perceive where he is coming from, we can know what lyrics from brother Paul we should listen to extra carefully to ensure that we are not mishearing.
In verse 14, Peter commands diligence, meaning we must exert ourselves and be zealous. He emphasizes robust and focused effort instead of offhandedly grabbing a line or two from Paul and believing our understanding is complete.
Peter urges us to “be diligent to be found by God in peace, without spot and blameless.” Since he is telling us to be diligent, it means that the spotlessness and blamelessness he has in mind are not what God imputes to us. Christ's righteousness was imputed to us when we accepted His blood, and then, in a legal sense, we became without spot and blameless.
But accepting Christ's blood did not require the diligence Peter talks about here. After we come under His blood, though, we must submit to God in living up to that imputed spotlessness and blamelessness. Doing so requires significant effort; thus, Peter uses “diligent.”
In verse 16, he warns that misusing Paul's words leads to destruction, a term frequently used concerning God's judgment on the disobedient. Jesus says that “wide is the gate and broad is the way that leads to destruction” (Matthew 7:13). In other words, the easy way does not end well. The future “man of sin” is called “the son of perdition [destruction]” (II Thessalonians 2:3), at least in part because he is destined for the Lake of Fire—his sins lead him to destruction. Earlier in the chapter, Peter warns of the fire that characterizes the coming day of judgment (evaluation against a standard) and destruction of ungodly men (II Peter 3:7). To summarize, then, the unstable and untaught will interpret Paul's teaching in such a way that will lead them into God's judgment—to destruction or perdition.
In verse 17, Peter adds another warning, this time against apostasy, or as he puts it, “fall[ing] from your own steadfastness, being led away with the error of the wicked.” He describes a change from a good spiritual state to a bad one.
The New King James Version uses the phrase “the wicked,” giving the impression that Peter is talking about deeply depraved people. However, the people the apostle describes do not have to be characterized as extreme at all. Several translations interpret the phrase as being “carried away with the error of the lawless.” The Greek word translated as “wicked” or “lawless,” athesmos (Strong's #113), indicates a person who is against what has been instituted as law, custom, ordinance, precept, or rule. The wicked do not have to be mass murderers but simply those who disregard the established standards. In this context, the established standards are the laws of God.
To summarize, Peter warns us to check ourselves regarding Paul's material so we are not led away by false teachers (the theme of Peter's previous chapter) or our own incorrect impression of what Paul says. If we fail to hear it correctly, we will fall into the error of those who disregard God's law, those who are ignorant of the whole counsel of God (“untaught”), and who thus are not steadfast (“unstable”). These individuals avoid the narrow way because they find it constraining, even though it leads to eternal life.
