Isn’t that such an interesting statement by Jesus in Matthew? Such a person will be called (by whom is not stated) least in the kingdom of heaven. But then, in the following sentence, unless your righteousness exceeds the scribes and Pharisees who were so scrupulous about rules, you won’t even enter the kingdom.
And what does Jesus do later? He goes on to make a special focus of the least and the little ones, upturning our expectations. “Truly I tell you, among those born of women no one has arisen greater than John the Baptist; yet the least in the kingdom of heaven is greater than he” (Matthew 11:11). In the final judgement, the king declares, “just as you did it to one of the least of these who are members of my family, you did it to me” (Matthew 25:40). They may be least, but they are not insignificant, nor are they outside the kingdom.
This isn’t to say that Jesus is praising those who relax a commandment. But he does give his church authority to do so (Matthew 16:19 and 18:18-20; see this other thread). The key seems to be that when we bind or loose, we should do it like Jesus. He gives us some examples directly after those words about the law and prophets enduring. He overturns much of what was written about oaths, the requirement to retaliate in kind, and the mission to destroy enemies (Matthew 5:33-48). In doing so he shows how the Scriptures endure: only when read in light of him.
That gets back to the dig Jesus includes in his very common, very rabbinical statement that the law endures. Jesus envelopes this widely-voiced platitude within “untils”:
For truly I tell you, until heaven and earth pass away, not one letter, not one stroke of a letter, will pass from the law until all is accomplished. (Matthew 5:18)
By contrast,
Heaven and earth will pass away, but my words will not pass away. (Matthew 24:35)