In response to the claim the apostolic teaching concerning the return of Jesus is a cleverly devised myth, Peter claims to be an eyewitness of “his majesty” (2 Peter 1:16b-18). Peter is referring to the Transfiguration of Jesus (Matt 17:1-8, Mark 9:1-8, Luke 9:28-36). In this well-known story, Jesus takes Peter, James and John to a mountain where the glory of God comes upon Jesus. God’s voice speaks, declaring Jesus to be his son and then Jesus speaks with Moses and Elijah.
In the Gospels the transfiguration calls attention to who Jesus really is: he is the Son of God and the fulfillment of both the Law (Moses) and the Prophets (Elijah). God’s voice sounding from a bright 
In 2 Peter, the writer claims to be an “eyewitness of his majesty.” The noun Peter chooses for “eyewitness”(ἐπόπτης) only appears here in the New Testament, but has the connotation of someone that makes very careful observations. For example, God sees everything (2 Macc 3:39; 7:35; 3 Macc 2:21; 1 Clem 59:3) or the Emperor (IPerg 381).
What Peter witnessed was “his majesty” (μεγαλειότης, v. 16). This noun is also rare in the New Testament, but it is used in Acts 19:27 when the pagan Demetrius the Silversmith described the “great goddess Atremis,” she might lose some of her “majesty” if Paul’s gospel is left to grow unchecked. The word therefore refers to something ultimately impressive or awe-inspiring even in the pagan world. A similar word appears in v. 17 (μεγαλοπρεπής), although this word appears in the LXX to describe God himself (Deut 33:26; Sirach 17:3, “the glory of his voice”).
It is perhaps unexpected that Peter would answer the objection concerning the second coming of Jesus with a reference back to the Transfiguration. But as Thomas Schreiner points out, the transfiguration follows a statement about seeing “the Son of Man coming in his kingdom” (Matt 16:28–17:13; Mark 9:1–13; Luke 9:27–36).
In Matthew 16:21-23 Jesus predicts his own death and resurrection for the first time, immediately after Peter has confessed his belief in Jesus as the Messiah. In response to the surprising prediction that God’s Messiah was going to be killed when he went to Jerusalem, Peter rebukes Jesus (v. 22), and Jesus’ rebukes Satan and calls Peter a hindrance!
Jesus then declares to his disciples they must be ready to “take up their cross and follow him” (Matt 16:24-28). To a first century Jew, “taking up one’s cross” meant to be crucified by the Romans! Jesus warns his disciples that he will he be executed in Jerusalem, but also they must be ready for the same treatment. The assumed context of 2 Peter is just before Peter literally “takes up his cross” and die on account of his faith in Jesus.
Peter is therefore presenting himself as a prophetic witness to a foretaste of the glory of the Son of Man and his kingdom. Having raised the issue of prophecy, he goes on to argue that the prophets are reliable because they were inspired by the Holy Spirit.
crucified (Acts of Peter). There is nothing historical in these stories since the point of Jesus’ prediction was only to tell Peter that his faith was not weak and that he would persevere all the way to the end.
culture. If you really cannot see well, you find yourself in difficult, embarrassing, or potentially dangerous situations. It is one thing to not be able to read a menu in a restaurant, for example, and quite another to not be able to tell one person from another. Worse yet, if you cannot see well enough to read street signs, driving a car becomes very dangerous.
said you would do, etc. Like blindness, forgetfulness can lead to embarrassment (who are you again?) but also to potential danger. Think of people who have serious problems remembering who they are, such as an amnesiac or a person suffering from Alzheimer syndrome. It might be dangerous for a person to be on their own because they have forgotten critically important information that will keep them out of danger.
Pursuit of virtue must be a strenuous effort on the part of the believer. “Make every effort” implies deliberate action. Someone might claim to be growing in godliness, but if there is no deliberate activity then the claim is empty. Imagine someone who claims to be trying to lose some weight, but they are not dieting or exercising. They are not really making “every effort” to lose weight! This is a bit like a “good faith effort” in modern English, but perhaps stronger. It means that the person really does make an honest effort to pursue virtue and godliness.
Strangers are not always welcome. Imagine this scene: you are traveling in England, and in some small village you have some car trouble so you stop at the local pub with a colorful name like “the Prancing Pony” or “The Drunken Duck” or my personal favorite, “The Skiving Scholar” (which is in Plymouth). As you walk up to the door, you can hear people talking, laughing, etc. But when you open the door and step inside, everyone goes silent and looks at you: you are different. You are an outsider and no good can come from an outsider (especially an American). Maybe you hear some muttering in the background about “tourists” as people just glare at you, waiting to hear what you want.
The first application he develops is the relationship of the believer to the government. This is a particularly difficult problem since Rome ruled Asia Minor, and most of Asia Minor encouraged the worship of the Empire and the Emperor as a show of loyalty.
It is unlikely that this persecution reached beyond the city of Rome, but the Greco-Roman world always looked at Jews with suspicion, and even more so the growing sect of Christians. If Karen Jobes is right and the letter of 1 Peter is written to Jewish Christians expelled from Rome by Claudius, then they are literally “strangers and aliens,” exiles from their home.