I don't understand this question.
Yes, because he hadn't established the new.
Fulfill, complete the prophecies.
Was fulfill in relation to commands? Are there commands of prophecy?
The new covenant does not appear to have a law associated with it.
Romans 2:15 NASB - 15 in that they show the work of the Law written in their hearts, their conscience bearing witness and their thoughts alternately accusing or else defending them,
Deuteronomy 30:10 NASB - 10 if you obey the LORD your God to keep His commandments and His statutes which are written in this book of the law, if you turn to the LORD your God with all your heart and soul.
1 Corinthians 10:11 NASB - 11 Now these things happened to them as an example, and they were written for our instruction, upon whom the ends of the ages have come.
Hebrews 10:16 NASB - 16 "THIS IS THE COVENANT THAT I WILL MAKE WITH THEM AFTER THOSE DAYS, SAYS THE LORD: I WILL PUT MY LAWS UPON THEIR HEART, AND ON THEIR MIND I WILL WRITE THEM," He then says,
Jeremiah 31:33-34 NASB - 33 "But this is the covenant which I will make with the house of Israel after those days," declares the LORD, "I will put My law within them and on their heart I will write it; and I will be their God, and they shall be My people. 34 "They will not teach again, each man his neighbor and each man his brother, saying, 'Know the LORD,' for they will all know Me, from the least of them to the greatest of them," declares the LORD, "for I will forgive their iniquity, and their sin I will remember no more."
The question deals with the new covenant and the teaching of Jesus. The phrase law of Christ appears in the New Testament writings twice. But it is not said to be associated with the new covenant, unless somehow by implication that is not apparent to me. So, the Law is spiritual. But did Jesus teach the spiritual aspect or part of the Law? Was what He taught new?
Because Jesus observed and taught the Law. There are spiritual implications to everything in the Law and to everything He taught.
What Jesus taught may be seen as an application of the Law to the heart and to a person's thought life, even before any sinful acts have been committed. That is, there is sin even in a thought.