Well, don't you think there are several things to consider here?
First of all, that we don't have all Jesus' NT revelation in the gospels, for he did not give revelation concerning his inauguration of the New Covenant, which made the Old (Sinaitic) Covenant obsolete.
(Heb 8:13)
Secondly, during the life of Jesus, God's people were still under the Mosaic Covenant and Law.
He would not be giving them at that time the terms of the New Covenant and the New Law of Christ
(1Co 9:21; Gal 6:2) which would not be put into effect until the completion of his sacrificial propitiation.
Remember, he also said at that time, ". . .because they sit in the seat of Moses, you must obey
and do everything that the teachers of the law and the Pharisees tell you." (Mt 23:2-3)
But that no longer applies in the NT under the New Covenant.
We are now under the law of Christ (1Co 9:21; Gal 6:2),
which is the law of love (Mt 22:37-40; Ro 13:8-10), written on our hearts (Heb 8:10),
and which fulfills (accomplishes) the law (Mt 22:37:40; Ro 13:8, 10)
because the Holy Spirit gives the believer to know how to love.
And so thirdly, we must consider the whole revelation of the NT (Mt 22:37-40; 1Co 9:21; Ro 13:8-10)
to correctly understand any of it.
(In advance, Elin, I couldn't quite tell if you were agreeing or disagreeing with me. But if you are agreeing with me in whole or in part, great. This post is addressed to those who disagree with me. If that's you, well then here is my response.)
So how then do we interpret Jesus telling His followers to follow the Law and to teach others the same thing forever. It sounds really nice and happy to use all sorts of references to the "New Covenant" to imply that we shouldn't follow the "Old Covenant".
But in reality, Jesus Himself always followed His Father's Law, and never spoke AGAINST following the Law.
He was circumcised as a Baby.
His mother offered up sacrifices for purity.
He told the Pharisess that though they tithed a tenth of even their smallest herbs, they had forgotten the weightier matters like justice mercy and faithfulness, and they should have practicing these without neglecting the tithe of even the smallest herbs.
He said in Matthew 5 that
1) He didn't come to do away with the law
2) Not one letter was ever to be destroyed
3) If you follow it and teach others to do so, you'd be the greatest in His Kingdom
4) If didn't follow it and you taught others not to, you'd be the least in His Kingdom.
Sure, there's the 1 word "fulfill" in there, but I would say that any accurate definition of the word "fulfill" needs to be in perfect agreement with the 4 points mentioned above.
If we believe in 1 God, in the OT Jesus Himself gave the Law, and Jesus Himself said that it was forever, and that Jesus Himself said that He never changes.
So then any interpretation of anything in Scripture has to fall in line with that same stance, or we run the risk of implying that God isn't the same yesterday, today and forever.
Again, just to be clear,
I'm not saying in any way that our obedience or lack thereof has any bearing on our salvation. The Law wasn't intended for that. The Law, and our obedience to it shows us how to live practically and spiritually, and show that we love Him because we want to obey His commands.