Jesus teaches us that the beatitudes constitute the new alliance between God and men and the arrival of the kingdom of God between men, Jesus is the new Moses who comes to bring us a new commandment. The beatitudes perfect the Law of Moses (Exodus 20:1-17) and introduce us to a new spiritual life, that is why our Lord Jesus explains to us: "Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them" Matthew 5:17.
The beatitudes Jesus explains to us constitute the impersonal or logical aspect of God, the beatitudes are the footprint that God left so that we recognize his glory and his work, so that we see the world with his eyes, that is why this new alliance cannot be changed: "For truly I tell you, until heaven and earth disappear, not the smallest letter, nor the least stroke of a pen, will by any means disappear from the Law until everything is accomplished" Matthew 5:18.
And through the beatitude Jesus teaches us, we enter the Kingdom of Heaven, the beatitude is to seek the correct and the best, the correct for the gift of righteousness (golden rule, Matthew 7:12) and the best for piety (constancy, firmness): "Therefore anyone who sets aside one of the least of these commands and teaches others accordingly will be called least in the kingdom of heaven, but whoever practices and teaches these commands will be called great in the kingdom of heaven" Matthew 5:19.
The Pharisees and the Doctors of the Law represented in the times of Jesus, that false spirituality tinged with appearances and rigid obedience to laws and customs, these men were enemies of Jesus and led men astray, that is why Jesus give an example of what not to do: "For I tell you that unless your righteousness surpasses that of the Pharisees and the teachers of the law, you will certainly not enter the kingdom of heaven" Matthew 5:20.