"Therefore you shall be perfect, just as your Father in heaven is perfect." (Matthew 5:48 WEB)
One of the problems with modern Christianity is the mainstream concept that "It is impossible to be perfect." In this sense, the word "perfect" is meant as never making any kind of mistake.
If you do anything from "failing a test" to "going over the speed limit by one mph/kph" then you have failed to be perfect.
Some Christians even consider any kind of mistake to be a sin, believing that something like "failing a test" is actually sinful. Under this definition, then certainly it is impossible to be perfect!
However, this definition of perfection is not God's definition, and it has never been.
We are including human standards of measuring our performance (which we created) instead of using God's standards. Essentially, we are using measures we created to gauge performance that we consider important, rather than what God considers important.
Failing a test created by people to measure some arbitrary performance will never be considered a sin by God.
"For that which is exalted among men is an abomination in the sight of God." (Luke 16:15 WEB)
Someone might say, "Not applying yourself" is a sin.
According to who? If someone is not sinning by not being an adulterer, thief, sexually immoral, drunkard, etc., and they are loving others as themselves, yet they fail on a test, then they are still perfect according to God's definition.
Now, "sloth" or "laziness" is considered to be a sin by many, but this sin has to do with the inaction of failing to do what is right as discussed James 4:17.
However, this sin has nothing to do with wasting our time or "not applying" ourselves by not studying. Rather, this sin is about "And if a brother or sister is naked and in lack of daily food, and one of you tells them, 'Go in peace, be warmed and filled;' and yet you didn't give them the things the body needs, what good is it? Even so faith, if it has no works, is dead in itself." (James 2:15-17 WEB)
Granted, there is value in education, and there is value in doing well on tests.
There is also value in obeying laws created by authorities. And there can be consequences for failing in these areas. However, failing to do well in these areas is not sinful, and mistakes do not equate to imperfection.
If someone needs immediate medical attention, are you going to obey the speed limit when trying to get to the hospital? Do you really think it would be a sin to break a human-created law in order to fulfill a God-created law?
So, what is God's definition of perfection?
Jesus says to be perfect.
He does not say try to be perfect, he tells us to be perfect.
According to Jesus, God's definition of perfection is loving without partiality, just as God loves without partiality:
"You have heard that it was said, 'You shall love your neighbor, and hate your enemy.' But I tell you, love your enemies, bless those who curse you, do good to those who hate you, and pray for those who spitefully use you and persecute you, that you may be sons of your Father who is in heaven. For he makes his sun to rise on the evil and the good, and sends rain on the just and the unjust. For if you love those who love you, what reward do you have? Don't even the tax collectors do the same? If you only greet your friends, what more do you do than others? Don't even the tax collectors do the same? Therefore you shall be perfect, just as your Father in heaven is perfect." (Matthew 5:43-48 WEB)
However, this loving without partiality is more than just "love." According to Paul, love fulfills God's law, because it is the opposite of sin.
"Owe no one anything, except to love one another; for he who loves his neighbor has fulfilled the law. For the commandments, 'You shall not commit adultery,' 'You shall not murder,' 'You shall not steal,' 'You shall not give false testimony,' 'You shall not covet,' and whatever other commandments there are, are all summed up in this saying, namely, 'You shall love your neighbor as yourself.' Love doesn't harm his neighbor. Love therefore is the fulfillment of the law." (Romans 13:8-10 WEB)
"For the whole law is fulfilled in one word, in this: 'You shall love your neighbor as yourself.'" (Galatians 5:14 WEB)
God's definition of perfection is simply to not sin by loving him first and people second.
And sin is not some arbitrary concept of making mistakes. Sin is a very specific list of "You shall not," that Paul summarizes for us in 1 Corinthians:
"Or don't you know that the unrighteous will not inherit the kingdom of God? Don't be deceived. Neither the sexually immoral, nor idolaters, nor adulterers, nor male prostitutes, nor homosexuals, nor thieves, nor covetous, nor drunkards, nor slanderers, nor extortioners, will inherit the kingdom of God." (1 Corinthians 6:9-10 WEB)
"Mistakes" are a part of the natural learning process created by God. You cannot learn if you cannot make mistakes.
God's definition of perfection is to fulfill the law, which is to be holy, righteous, and sinless. According to John, this is a necessity for Christians:
"Whoever is born of God doesn't commit sin, because his seed [Jesus] remains in him; and he can't sin, because he is born of God." (1 John 3:9 WEB)
According to John, by definition, a Christian is someone who does not sin and cannot sin. This is because a true Christian has truly repented and now has God's Spirit within (born of God).
The whole purpose of Jesus' sacrifice is so that our past sins can be forgiven (Romans 3:25; 2 Peter 1:9) so that we can be considered righteous when we obey the law (Romans 2:12-29).
"For he who lacks these things is blind, seeing only what is near, having forgotten the cleansing from his old sins." (2 Peter 1:9 WEB)
"If therefore the uncircumcised keep the ordinances of the law, won't his uncircumcision be accounted as circumcision? Won't the uncircumcision which is by nature, if it fulfills the law, judge you, who with the letter and circumcision are a transgressor of the law? For he is not a Jew who is one outwardly, neither is that circumcision which is outward in the flesh; but he is a Jew who is one inwardly, and circumcision is that of the heart, in the spirit not in the letter; whose praise is not from men, but from God." (Romans 2:26-29 WEB)
Paul says that a true Jew (God's people) is the one who "keep the ordinances of the law" which is keeping God's commandments.
"Circumcision is nothing, and uncircumcision is nothing; but obeying the commandments of God is everything." (1 Corinthians 7:19 NRSV)
Absolutely never has God's definition of perfect ever meant that people cannot make mistakes. God's definition of perfect is equivalent to being holy and righteous.
"...be diligent to be found in peace, without blemish and blameless in his sight." (2 Peter 3:14 WEB)
The sacrifice of Jesus Christ washes away past sins (Romans 3:25; 2 Peter 1:9). That is not to say that Jesus' sacrifice won't wash away your future sins, but that there should come a point when you truly repent (at which point you should not have any more future sins). If you are not sinning, then you are living "without blemish and blameless in his sight." (2 Peter 3:14 WEB)
Are you doing any of these sins in 1 Corinthians 6:9-10?
Sexually Immoral (Adulterer, Homosexual)
Thief (Covetous – always desiring what you don't have. Greed)
Drunkard (Being drunk, not just drinking, which is something Jesus did.)
Slanderer (False witness)
Extortioner (Black Mail; Threats)
Or are you doing any of these additional sins listed in Galatians 5:19-21?
Hatred, Strife, Jealous, Outburst of Anger, Rivalries
If you are not doing any of these things, then by God's definition you are living righteously, and with the sacrifice of Jesus Christ you are considered perfect.
Do you give to the poor and love your neighbor as yourself?
Jesus told one man, "If you want to be perfect, go, sell what you have, and give to the poor, and you will have treasure in heaven; and come, follow me." (Matthew 19:21 WEB)
Why would Jesus tell someone they could be perfect, if it was impossible?
Rather, it is expected. This is Jesus talking here, the same Jesus who died for our sins. We can be perfect in God's eyes through our faith as shown through our actions, by not sinning and loving others.
"Even so faith, if it has no works, is dead in itself." (James 2:17 WEB)
Conversely, if you are doing any of these sins listed above, then stop.
Of course, it is always easier to say than do, but no one is making you sin. You are choosing to sin every time you do.
"Let no man say when he is tempted, 'I am tempted by God,' for God can't be tempted with evil, and he himself tempts no one. But each one is tempted, when he is drawn away by his own lust, and enticed." (James 1:13-14 WEB)
Personal pleasure is a primary source of sin – it means we love ourselves more than we love God.
"For men will be lovers of self, lovers of money, boastful, arrogant, blasphemers, disobedient to parents, unthankful, unholy..." (2 Timothy 3:2 WEB)
Think about all the sins you are not doing right now. For most people, if they look at the list above, there is probably just one sin they have a problem with. All the other sins are not a problem.
Maybe your only vice is sexual immorality – you don't steal, drink, lie, or hate. Or maybe your only sin is being a drunkard – you don't have issues with sexual immorality, stealing, lying, or hating.
Maybe you do have problems with multiple sins, but there is the same solution no matter how many sins you struggle with: Start loving God more than you love yourself.
This is the key to repentance and salvation. Learn to love God more than you love yourself. Do this, and you will live eternally.
Think about Christian martyrs who are faced with the choice of death or denying Christ. By choosing death, you are choosing to love God more than your own life...Maybe you think you could do this? Yet you won't choose to love God more than your personal pleasure you get from your sexual immorality?
"If any man desires to come after me, let him deny himself, and take up his cross, and follow me." (Matthew 16:24 WEB)
"He who loves father or mother more than me is not worthy of me; and he who loves son or daughter more than me isn't worthy of me. He who doesn't take his cross and follow after me, isn't worthy of me." [Meaning, he who loves self more than Jesus isn't worthy of Jesus.] "He who finds his life will lose it; and he who loses his life for my sake will find it." (Matthew 10:37-39 WEB)
If you can't choose loving God over your own lusts, then you probably won't choose God if faced with death, which means you won't be going to heaven when you do die.
"Be faithful to death, and I will give you the crown of life." (Revelation 2:10 WEB)
"How narrow is the gate, and restricted is the way that leads to life! Few are those who find it." (Matthew 7:14 WEB)
Again, this is Jesus speaking here, the same Jesus who died for our sins. Loving God more than ourselves is the key to repentance and salvation. Do this, and you will live eternally with Jesus Christ, who modeled this for us:
"Nevertheless, not my will, but yours, be done." (Luke 22:42 WEB)
"You ought to live holy and godly lives as you look forward to the day of God..." (2 Peter 3:11-12 NIV)
"Make every effort to be found spotless, blameless and at peace with him." (2 Peter 3:14 NIV)