See this passage explained in the notes at Matthew. 15:1-20.

Came from Jerusalem - Probably to observe his conduct, and to find matter of accusation against him.

Came from Jerusalem - Probably for the express purpose of disputing with Christ, that they might entangle him in his talk. Malice and envy are never idle - they incessantly hunt the person they intend to make their prey.

Then (1) came together unto him the Pharisees, and certain of the scribes, which came from Jerusalem.
(1) None resist the wisdom of God more than they that should be wisest, and they resist because of their zeal for their own traditions: for men please themselves in superstition more than in any other thing, that is to say, in a worship of God fondly devised by themselves.

Then came together unto him the Pharisees,.... Having heard of his miracles, and that he was come into the land of Gennesaret; they consulted with one another, and came together to Jesus, to watch and observe what was said and done by him, and take what advantage they could against him. These were not of that country, but were of Jerusalem, as were their companions the Scribes:
and certain of the Scribes, which were of Jerusalem; for the fame of Christ had reached the metropolis of the nation; and these men being the more artful and cunning of the whole sect, either came of themselves, or were sent by the sanhedrim, to make their observations upon his doctrine and conduct; See Gill on Matthew 15:1.

One great design of Christ's coming was, to set aside the ceremonial law; and to make way for this, he rejects the ceremonies men added to the law of God's making. Those clean hands and that pure heart which Christ bestows on his disciples, and requires of them, are very different from the outward and superstitious forms of Pharisees of every age. Jesus reproves them for rejecting the commandment of God. It is clear that it is the duty of children, if their parents are poor, to relieve them as far as they are able; and if children deserve to die that curse their parents, much more those that starve them. But if a man conformed to the traditions of the Pharisees, they found a device to free him from the claim of this duty.

Then came together unto him the Pharisees. This sharp controversy, which contains the sharpest rebuke that Christ had thus far paid to the Pharisaical system, is recorded also by Matthew. 15:1-20, where see notes. Mark, for the benefit of Gentile readers, adds a few words concerning Jewish customs.
Come from Jerusalem. Probably formally sent by the Sanhedrim to investigate the work and teaching of Jesus.

Coming from Jerusalem - Probably on purpose to find occasion against him. Matthew 15:1.