Matthew 5:17-20
The Fulfillment of the Law
17 "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. 18 I tell you the truth, until heaven and earth disappear, not the smallest letter, not the least stroke of a pen, will by any means disappear from the Law until everything is accomplished. 19 Anyone who breaks one of the least of these commandments and teaches others to do the same 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. 20 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.
Jesus tells his followers He did not come to abolish Mosaic Law in the Old Testament, but to fulfill it...Jesus IS the Bible, therefore he does fulfill it, both Old and New Testament...The Old Testament Law will not disappear until everything is accomplished in the Old Testament Law... So all we read in the Old Testament Law will be fulfilled...
The Old Testament is difficult to understand, as is some parts of the New Testament, as Peter points out in reference to Paul's letters...But, even though we have difficulty in understanding certain scriptures, our righteousness must surpass that of the Pharisees and the teachers of the law, if we want to enter God's grace and enter the kingdom of heaven...This is also difficult to understand, because Paul tells us we are saved by God's grace and not by are work's...That being said we must be good, so God will look at us with His grace like He looked at Noah (and look at us in the same light), with favor...