2 + 2 = 5

 "I have spoken to you of earthly things and you do not believe; how then will you believe if I speak of heavenly things?" John 3:12

If you believed that 2+2=5, how would that affect transactions you engaged in requiring mathematical calculations? Nothing would function properly. Your bank ledger would not balance. You would put the wrong amounts of ingredients in your recipes. The things you build would not be structurally sound. And so on. Jesus Christ admonished the disciples because they could not figure out His physical examples were used to explain spiritual truths. This continues to this day. Christians struggle with God's apparent lack of revelation regarding scripture, the circumstances of their lives, and current events. The reason may be that they don't understand the things God has revealed in scripture. So, how can He reveal further truths that depend on them understanding the things He has already shared? Nowhere is this problem more obvious than when it comes to the differences between the Old and New Covenants. Here are a few examples of this problem that I have experienced.

New Covenant

Many Christians believe the New Covenant begins with the Gospels of Matthew, Mark, Luke, and John. It could be due to them equating the birth of Jesus  Christ with the beginning of the New Covenant or because most Bibles separate the covenants at the start of the Gospels. Therefore, they end up believing that things like the Sermon on the Mount is the Lord giving Christians the standard by which to live their lives. That repeating the words to the "Lord's Prayer" is praying to God. And other incorrect assumptions have led to a myriad of beliefs permeating the body of Christ. 

However, the New Covenant began after the death of Jesus Christ. Hebrews 9:16-17 says, "In the case of a will, it is necessary to prove the death of the one who made it, because a will is in force only when somebody has died; it never takes effect while the one who made it is living." A will is another way of saying covenant. An inheritance is not received until after a person dies. Therefore, the New Covenant did not take effect until after the death of Jesus Christ. Understanding this truth will determine how one rightly divides the scriptures. This goes a long way in how they approach the Christian life.

Forgiveness 

When you don't understand where the separation between the two covenants is you will not understand forgiveness. How often have you heard Matthew 6:14-15 referenced as evidence to support how God views us in light of His forgiveness? Jesus says, "For if you forgive other people when they sin against you, your heavenly Father will also forgive you. But if you do not forgive others their sins, your Father will not forgive your sins." This is Jesus burying His audience under the impossible requirement to forgive everyone who has ever sinned against you or else God will not forgive you. The only conclusion that can be reached is that your sins will never be forgiven by God. Besides, how will you know? Nobody has kept track of every sin committed against them. If you did, how long would it take to track all of these people down? What if they are no longer alive? Plus, how does God notify you that you're forgiven? Do you see how difficult this becomes?

After Jesus died on the cross, the forgiveness issue between man and God is over. In Ephesians 4:32 Paul writes, "Be kind and compassionate to one another, forgiving each other, just as in Christ God forgave you." Do you notice the difference? We are told to forgive others because God has already forgiven us. We don't forgive others prior to receiving God's forgiveness. That is a huge difference that is often unrecognized by Christians. Not only are you free to forgive others who sin against you, but the separation between you and God is gone. You now have access to your God because He is no longer counting your sins against you. Your entire Christian life changes. No more doing penance. No more bloodless sacrifices. No more streaming down aisles to rededicate your life again. No more keeping of short accounts. No more making appointments to see the priest in the confession booth. No more saying the Lord's Prayer endlessly. No more fear of God. It is finished!

Tithing

The subject of tithing is taken for granted. For the majority of Christians, it is a given that tithing is as central to the Christian life as the death and resurrection of Jesus Christ. One of the passages used to support this belief is Matthew 23:23. There Jesus said, "Woe to you, scribes and Pharisees, hypocrites! For you pay tithe of mint and anise and cummin and have neglected the weightier matters of the law: justice and mercy and faith. These you ought to have done, without leaving the others undone." Who was Jesus talking to? He was talking to scribes and Pharisees, not to Christians. The scribes and Pharisees were Jewish leaders who taught the Old Covenant law. They weren't elders and pastors teaching New Covenant grace. Furthermore, Jesus was talking about their lack of love, not their tithing record. 

Tithing was done to support the Levitical Priesthood, not your local church. Under the New Covenant, there is no law requiring us to give a tithe of our income to a church or ministry, much less the Levitical Priesthood that no longer exists. The New Covenant teaches that "Each of you should give what you have decided in your heart to give, not reluctantly or under compulsion, for God loves a cheerful giver (2 Corinthians 9:7)." When you are required to do something it can lead to being reluctant to give because you may not have the resources available or you don't want to do it. Under the New Covenant, God has set us free to decide what it is we want to give and to whom we want to give it. It is the difference between giving to get something from God and giving from a heart that has been given everything by God. 

Conclusion

When your premise is off your findings will be off. In mathematics, this is discovered quickly as you get wrong answers. However, when your premise is based on the Old Covenant what you will find is that you are living a life you cannot live as you try to get things from God He never promised to give you and missing out on those things He has freely given to you through faith in Jesus Christ. You will spend your life trying to live under a Covenant given to the Jewish nation that they could not obey. You won't understand those things that God has given to you as an inheritance of your faith. As a Christian author, Major Ian Thomas writes, "There are those who have a life they never live. They have come to Christ and thanked Him only for what He did, but do not live in the power of who He is. Between the Jesus who "was" and the Jesus who "will be" they live in a spiritual vacuum, trying with no little zeal to live for Christ a life that only He can live in and through them, perpetually begging for what in Him they already have!"