Matthew 5:17-19: "Do not think that I came to destroy the Law or the Prophets. I did not come to destroy but to fulfill. "For assuredly, I say to you, till heaven and earth pass away, one jot or one tittle will by no means pass from the law till all is fulfilled." Whoever therefore breaks one of the least of these commandments, and teaches men so, shall be called least in the kingdom of heaven; but whoever does and teaches them, he shall be called great in the kingdom of heaven."

The overall context Jesus is giving in the Sermon is a contrast of his correct interpretation of the law to the Pharisees misinterpretation. That the Pharisaic traditions negated the law because they would reinterpret it, not practicing it in the way Moses had intended. Jesus is conveying to the people that his intent is to fulfill the law as Moses had written it. As long as Jesus was alive he had to keep the law the way it was written, until he dies and raises again and ratifies what is needed to be kept under the law of Christ (not Moses). This law was either given directly by Jesus or through the apostles after the resurrection.

A jot and tittle were the smallest strokes of the Scribes pen in writing the Scripture (in the Hebrew alphabet). The smallest Hebrew letter, a 'yod' is what Jesus had in mind when He was explaining the Old Testament. This refers to the stroke involved in writing just part of a letter (such as the cliché crossing one's 't's in English).  The smallest "jot or tittle" of "the law and the prophets" will not pass away, meaning the least of all the law, which is incorporated in all 613 laws. This would include all the ceremonial laws!

If one insists on continuing to keep the 10 then it means we would have to keep all the Torah laws that Israel kept, there would be no change from the old to the new covenant. So this must have another meaning.

Matt 5:17 "Do not think that I came to destroy the Law or the Prophets. I did not come to destroy but to fulfill.
  This apparent dispute is solved in the meaning of to fulfill, which means to bring to completion, to put aside. Christ did not say: "I come to lengthen the law," to extend its usage. He said: "to fulfill" meaning to bring it to its completion or goal (telios), to fill up - to a complete measure. It is the same word used for the prophecies he fulfilled, and he explains the meaning afterwards.

The Sermon on the Mount is mistakenly used to prove one is still under the law but Jesus is only explaining the true intent of the law in contrast to what the Pharisees taught on it.

Jesus also said in Mt.5:19 “Whoever therefore breaks one of the least of these commandments, and teaches men so, shall be called least in the kingdom of heaven”

What would be the least of the commandment’s? This would include the ceremonial not the 10 only. Because all of them were still in effect when he spoke this. And that is the point, it is negating the commands they were under at the time. The law was a unit from the least to the greatest of the commandments.

The word fulfill is key. Matthew consistently uses the word fulfill in a specific manner, once something is fulfilled there is not a future fulfillment. He quotes Isa.7:14 for the fulfillment of the virgin birth. Where he was to be born Micah 5:2 there is no waiting for this to occur in the future. To fulfill something means to bring something to a completion. It is used of prophecy which Jesus fulfilled.

Matt 1:21-22 “So all this was done that it might be fulfilled which was spoken by the Lord through the prophet,

Matt 2:23 “And he came and dwelt in a city called Nazareth, that it might be fulfilled which was spoken by the prophets, “He shall be called a Nazarene."”

Matt 4:13-14 “that it might be fulfilled which was spoken by Isaiah the prophet, saying:

Matt 8:17 “It might be fulfilled which was spoken by Isaiah the prophet”

Matt 12:16-17 “that it might be fulfilled which was spoken by Isaiah the prophet, saying:

Jesus fulfilled all the laws requirements by his perfect obedience throughout his life, taking upon himself the penalty and the curse of the law and with his dying rendered it inoperative for the believer (Rom.10:4-5; Heb. 8:17). To say one is going to keep the law because of the Old Testament requirement, is to ignore the work that Christ did in our stead.

Jesus after the resurrection continued with the apostles for 40 days.

Acts 1:2-5 “Until the time he was taken up after he through the Holy Spirit had given commandments to the apostles he had chosen." "To whom He also presented Himself alive after His suffering by many infallible proofs, being seen by them during forty days and speaking of the things pertaining to the kingdom of God. And being assembled together with them, V.4-5 “He commanded them not to depart from Jerusalem, but to wait for the Promise of the Father, "which," He said, "you have heard from Me; "for John truly baptized with water, but you shall be baptized with the Holy Spirit not many days from now."

An interesting correlation is that Jesus stayed with the apostles 40 days giving instruction and commandments, the same amount of time Moses was on Sinai receiving the commandments from God.

Commands are something God gives at a certain time. They are not to be confused as to always being kept. There are many commandments that are no longer applicable.

Acts 1:4 He commanded them not to depart from Jerusalem, but to wait for the Promise of the Father, Luke 24:49"Behold, I send the Promise of My Father upon you; but tarry in the city of Jerusalem until you are endued with power from on high."

If we are going to keep everything he spoke we would always have to go to Jerusalem to receive the Holy Spirit. Some commands are specific and one time events. Some are temporary such as the sacrifices, others still continue. Some are to certain individuals, others are to the whole Church.  For example being still under the law before his resurrection they would sacrifice animals. After he died, the veil was rent and his sacrifice was once for all, they no longer had to do continue sacrificing.

What of his instructions in Matt 28:20:"teaching them to observe all things that I have commanded you; and lo, I am with you always, even to the end of the age." Amen. When Mt.28 states to observe all things that I have commanded you must include what he spoke to the disciples after his resurrection. Which could explain the very fact of why he stayed 40 days and did not ascend to heaven immediately. Acts 1:1-2 The former account I made, O Theophilus, of all that Jesus began both to do and teach, until the day in which He was taken up, after He through the Holy Spirit had given commandments to the apostles whom He had chosen,” He was giving new commands that would supercede the others under the law. These were taught to the church in the epistles.

So then what is the law good for? 

Paul tells us what the laws usage is for, and it is not for the believers to keep-

1 Timothy 1:8-11: “But we know that the law is good if one uses it lawfully, knowing this: that the law is not made for a righteous person, but for the lawless and insubordinate, for the ungodly and for sinners, for the unholy and profane, for murderers of fathers and murderers of mothers, for manslayers, for fornicators, for sodomites, for kidnappers, for liars, for perjurers, and if there is any other thing that is contrary to sound doctrine, according to the glorious gospel of the blessed God which was committed to my trust.”

This is how we use the law, we are told to preach Christ and use the scripture to present the gospel to people that do or do not recognize their sinners.