Peter probably got the wind knocked out of him during Christ’s prediction regarding his death in v.18 and was thinking—“That doesn’t sound ideal.” And then he turns around and sees John in tow and asks Christ: “What about that guy? What’s going to happen to him?” Maybe he’s thinking that he could feel better about his destiny if John’s sounded just as bad or worse.
No matter what, Jesus is aware of the self-centered motive in this question, so in v.22, he reorients Peter’s thoughts back to what is important—“It really doesn’t affect you even if he lives on far past your days; you can just concern yourself with following me by trusting in what I have done and what I have told you. If I want something different for him, what does that matter to you?”
We can get ourselves in so much trouble by being consumed with what God is doing in other’s lives. If our thoughts along those lines are left unchecked, then we will begin to adopt the mindset that life isn’t fair and God is out to get us; and that although he loves all Christians, he has a special love and abundant blessings for some Christians.
Truth be told, oftentimes our assessment is vastly skewed in these things, meaning that we really don’t have an accurate picture of the reality of the situation. Nevertheless, we compare marriages, we compare children, we compare financial status, we compare health, we compare schedules and wouldn’t you know it, in all of our comparisons we always conclude that we received the short end of the stick.
In the end, it’s directly charging God with injustice: “That’s not fair!”
There’s only one word that describes what this is and that word is jealously. James speaks very directly to this in James 3:14 But if you have bitter jealousy and selfish ambition in your heart, do not be arrogant and so lie against the truth. 15 This wisdom is not that which comes down from above, but is earthly, natural, demonic. 16 For where jealousy and selfish ambition exist, there is disorder and every evil thing.
Jealousy is directly tied to selfish ambition because jealousy seeks that which promotes oneself and therefore it is directly opposed to the truth because to embrace the truth is to say that Jesus has saved us from our self-centeredness. To seek to promote oneself is worldly and demonic and leads to great evil and disorder.
This means that those whose lives are always chaotic with self-inflicted consequences, possess a refusal to trust and rest in God’s purposes and instead seek to promote oneself in its place. This takes on a variety of manifestations, but it’s fairly easy to spot because they always disregard certain parts of God’s revealed will in order to follow their own desires. Ungodly comparisons will always get us into trouble and completely hinder usefulness for Christ.