C.S. Lewis was a great thinker and a genius in the use of words. When talking about the perfection Jesus called disciples to at the end of Matthew 5, Lewis said,
"The command "Be ye perfect" is not idealistic gas. Nor is it a command to do the impossible. He is going to make us into creatures that can obey that command. He said (in the Bible) that we were "gods" and He is going to make good His words. If we let Him –for we can prevent Him, if we choose –He well make the feeblest and filthiest of us into a god or goddess, dazzling, radiant, immortal creature, pulsating all through with such energy and joy and wisdom and love as we cannot now imagine, a bright stainless mirror which reflects back to God perfectly (though, of course, on a smaller scale) His own boundless power and delight and goodness. The process will be long and in parts very painful; but that is what we are in for. Nothing less. He meant what He said."
I like the words "idealistic gas" which is how I think many people view all of the work of God and blessings He promises in the lives of His children. We are to be comforted from the God of comfort, but many do not have this comfort and so they dismiss the reality of the blessing. God wants us to rejoice and be joyful because we are redeemed, but many do not have joy and so they doubt the reality of the promise. To so many, I think that the blessed Christian life is viewed as nothing more than "idealistic gas" with the hopes of maybe having these to be a reality in the afterlife.
But what about the words of Paul in Philippians 4 that says "the peace of God will guard your hearts and your minds in Christ Jesus"? There are so many Christians who do not have this and so to them how can the promise be more than "idealistic gas"?
Lewis was talking about the command that disciples being perfect as God is perfect. It means that we stop sinning, stop the prejudicial, biased and carnal offering of love to only a select few, and to start loving even our enemies. God means what He says. God wants us to love all men, even the ones that are evil scoundrels as hard as that is - which is the point.
And you shall be perfect as He is perfect.