The promises made to Abraham included land, material blessings, and protection. Those who are Christ's now have the hope of partaking of those promises, and of ruling the world with Jesus Christ. That rule will be a perfect and righteous rule, and in order to enjoy all those things one would need to be given life in the Age To Come. Yet Jesus said that unless our righteousness exceeded the righteousness of the Pharisees, we would in no wise enter the Kingdom of God (Matthew 5:20). This hearkens back to verses like Psalm 15:1-2, that the one who would dwell in God's holy tabernacle is the one who works righteousness and speaks the truth in his heart.
God is a righteous judge and His judgment is perfect. His standards often sound harsh or strict, but that's because it is a much higher standard than any that we go by in our lives. Yet His righteous judgment is balanced by His tender mercy and compassion. II Peter 3:9 says, "The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance." God's judgment will come to pass, but He has been waiting to allow more people to come to repentance and accept the grace and mercy He made available through His Son's sacrifice.
Under the dispensationalist system I was taught that in the administration of the Law, salvation was based on works, while in the current administration it is based on grace. However, Paul said that no flesh shall be justified by the works of the Law (Romans 3:20). The Law was given to Israel as an illustration of what living by God's standards should look like for them, in their situation. It also served to keep them separate from the surrounding pagan nations. But the problem was that no one could live up to those standards. God knew this and in His grace and mercy made provision for them by giving them a system of sacrifices and offerings, which temporarily covered their sins and also pointed to the ultimate sacrifice which was to come. But even more than covering their sins, God's desire was for their hearts to be righteous so they wouldn't sin in the first place. This is spoken of in the Old Testament.
Jesus also spoke of the importance of what was in one's heart, even more than obeying the letter of the Law. On two recorded occasions (Matthew 9:13 and 12:7) he quoted Hosea 6:6, "I desire mercy and not sacrifice." He redefined the Law, raising it to a higher, spiritual level. This is both good news and bad news for us. The good news is that we're not bound by the minute details of the Law. For example he taught that it was more important to heal or to do something helpful on the Sabbath, than it was to obey the letter.
Part of the problem with trying to keep the letter of the Law was that often unique situations require unique handling. If a man has a sheep that falls into a ditch on the Sabbath, he would certainly pull it out, even though that would be work. Is it work to get something to eat on the Sabbath? Jesus and his disciples picked grain and were criticized for it. But he reminded them that the priests work on the Sabbath yet are not blamed. The point of the Sabbath was to keep God first, and to remember how He led them out of captivity in Egypt (Deuteronomy 5:12-15). Can you not do that and still take care of your livestock or prepare a meal? He said that the greatest commandment was to love God with all your heart, soul, mind, and strength. If you truly love God with all your heart, you will naturally want to do what pleases Him.
Jesus demonstrated God's grace and mercy by his inspired reply to those accusing the woman caught in adultery. While it was true that the Law said she should be stoned, he said to them, "He that is without sin among you, let him first cast a stone at her" (John 8:7). He ate with publicans and sinners and befriended the outcasts of society, demonstrating God's compassion which was lost to the legalists who only obeyed the letter of the Law. He said the second great commandment was to love your neighbor as yourself. If you are truly loving your neighbor you will not want to sin against him. The true heart behind the Law was to love God and love your neighbor. "On these two commandments hang all the law and the prophets" (Matthew 22:40).
However there was also bad news in Jesus' higher standards. The Law said we should not kill. But Jesus took it even further and said that if we are merely angry with a brother, we are just as guilty as if we had committed murder (Matthew 5:21-22). Most of us have not murdered anyone, but who can say they were never angry? Who can say they have never thought evil of another person? By the Law of Moses we were guiltless as long as we didn't act on our desire to harm someone. But by Jesus' standard, the very desire was as bad as doing it. Likewise, the Law said not to commit adultery. But Jesus said that anyone who looks at a woman with lust is guilty of adultery (Matthew 5:27-28). We may refrain from doing the act, but who can say they have never desired it in their heart?
The Law said "an eye for an eye, and a tooth for a tooth." The original purpose behind this was to limit the response to evil, so they wouldn't go overboard with retaliation. Yet Jesus said we are not to retaliate at all when someone does evil to us, but to turn the other cheek (Matthew 5:38-43). However, even if we do not retaliate, who can say that they would not want to? And the desire is as bad as the act itself. Similarly, if I were to take literally Jesus' command to pluck out my eye if it caused me to sin (Matthew 5:29-30), which is an example of using an extreme case to make the point, would it solve the root problem? The point of the command is to be willing to do whatever it takes to avoid sin. But if I did not have my eyes to look at another with lust, would that get rid of the lust in my heart?
As if that weren't enough, Jesus spoke of not only loving our friends but even loving our enemies (Matthew 5:43-48). Even unbelievers love those who love them. But loving someone who hates you is a whole new concept for most. And yet even if I were to go through the motions and do some good work out of obligation and not out of love, I am no better than the hypocrites that Jesus spoke of (Matthew 6:1-4). Genuine Godly love like this must be in the heart and not just put on superficially. "A good man out of the good treasure of the heart bringeth forth good things: and an evil man out of the evil treasure bringeth forth evil things" (Matthew 12:35).
James taught the same thing in his epistle. He said, "If ye fulfil the royal law according to the scripture, Thou shalt love thy neighbour as thyself, ye do well" (James 2:8). Some have erroneously taught that James was encouraging the keeping of the Law of Moses. But he refers to the "royal law" here (and also the "law of liberty" in 1:25 and 2:12), not the Law of Moses. The context of these passages shows that he is referring to the same concept that Jesus spoke of, that the whole Law hangs on the two great commandments, to love God and to love your neighbor (Matthew 22:37-40). The Apostle Paul also wrote that love is the fulfilling of the Law (Romans 13:8, 10; Galatians 5:14). This heart of love is what God is more interested in than our keeping the minute letter of the Law, since people could observe legalistic rules and not walk in love.
Because of my dispensationalist background, I used to believe that when Jesus taught anything that had to do with actions or behaviors, it must be "addressed to a different administration," because we are saved by grace and not by works. Thus the Gospels were "not addressed to us" and consequently there was little emphasis on the Gospels compared to the Epistles. As a result Jesus was separated from his words, which the Scriptures tell us are the key to eternal life (John 3:34; 6:63; 12:47,48; 14:23; 15:7; I Timothy 6:3,4). But as one can see, he wasn't teaching salvation by works, he was teaching that God was interested in works which were motivated by a heart of love. In my old background, it was taught that the Law Administration continued until the end of the Gospel period. But Jesus said, "The law and the prophets were until John: since that time the kingdom of God is preached, and every man presseth into it" (Luke 16:16). The Kingdom of God which Jesus preached will be one in which the ways of God, and the love of God, will prevail, rather than the outdated Law of Moses. And we are called to aspire to that standard in anticipation of that coming age.
However, even if we love God, we are not perfect, and we still sin. When Jesus took the Law further (don't be angry, don't look at a woman with lust, cut off whatever members cause you to sin, etc.) was he laying out a higher level of rules for us to follow? Do we just exchange one set of laws for another which is even harder to keep? This cannot be the case. Jesus sums up his standards by saying, "Be ye therefore perfect, even as your Father which is in heaven is perfect" (Matthew 5:48). How can that be possible? How can God expect us to be perfect? And if we have to be perfect to enter the Kingdom of God, who can be saved? The disciples asked this very question in Matthew 19:25-26, and the Lord's answer was, "With men this is impossible; but with God all things are possible."
God promised that one day all the world will be governed by these principles. The Messiah would come and rule in righteousness, and observe all of God's ways, and the saints who rule with him will likewise judge righteously, according to God's standard which includes grace, mercy, and love, as well as perfect holiness. In the meantime, however, the heart of man is selfish and wicked. The only way to achieve the true righteousness of the heart that Jesus spoke of in his teachings is to get a new heart, which is only possible with the power of God. This is the purpose of the new birth and the holy spirit.