See also Mark 7:15-17.

And he called the multitude - In opposition to the doctrines of the Pharisees, the Saviour took occasion to show them that the great source of pollution was the heart. They supposed that external things chiefly defiled a man. On this all their doctrines about purification were founded. This opinion of the Jews it was of great importance to correct. The Saviour took occasion, therefore, to direct the people to the true source of defilement - their own hearts. He particularly directed them to it as of importance - "Hear and understand."

Hear and understand - A most important command. Hear - make it a point of conscience to attend to the ministry of the word. Understand - be not satisfied with attending places of public worship merely; see that the teaching be of God, and that you lay it to heart.

And he called the multitude,.... Having silenced the Scribes and Pharisees, and judging it not worth his while to say any more to men so obstinate and perverse; who were not open to conviction, nor would attend to any argument or reason, though ever so clear and strong, against their darling notions; he leaves them, as both disliking them, and despairing of them, and calls to the common people; who, through their great veneration for these men, upon their coming withdrew, and stood at a distance; nor indeed would they admit them very near unto them, lest they should be polluted by them: Christ, I say, calls to these to come nearer to him, hoping better of them, and knowing that they were more tractable, and teachable; and that there were some among them, that were to be brought off of their former principles and prejudices, to embrace him, and the truths delivered by him:

and said unto them, hear and understand; this he said, partly, by way of reflection upon the learned Scribes and Pharisees, who, with all their learning, could not hear him so as to understand him; and partly to excite the attention of the multitude to what he had to say; as also to show, that barely to hear with the outward hearing of the ear, will be of no service, unless what is heard is understood; and that the way to understand, is to hear.

{4} And he called the multitude, and said unto them, Hear, and understand:

(4) Christ teaches us that the hypocrisy of false teachers who deceive our souls is not to be endured at all, not even in small matters, and there is no reason why their office or position should blind our eyes: otherwise we are likely to perish with them.

15:10 He called the multitude. In order to show them that the Pharisaical expounders of the law did not understand its real sense.

10. And he called the multitude, and said unto them-The foregoing dialogue, though in the people's hearing, was between Jesus and the pharisaic cavillers, whose object was to disparage Him with the people. But Jesus, having put them down, turns to the multitude, who at this time were prepared to drink in everything He said, and with admirable plainness, strength, and brevity, lays down the great principle of real pollution, by which a world of bondage and uneasiness of conscience would be dissipated in a moment, and the sense of sin be reserved for deviations from the holy and eternal law of God.

Hear and understand:

15:10-20 Christ shows that the defilement they ought to fear, was not from what entered their mouths as food, but from what came out of their mouths, which showed the wickedness of their hearts. Nothing will last in the soul but the regenerating graces of the Holy Spirit; and nothing should be admitted into the church but what is from above; therefore, whoever is offended by a plain, seasonable declaration of the truth, we should not be troubled at it. The disciples ask to be better taught as to this matter. Where a weak head doubts concerning any word of Christ, an upright heart and a willing mind seek for instruction. It is the heart that is desperately wicked, Jer 17:9, for there is no sin in word or deed, which was not first in the heart. They all come out of the man, and are fruits of that wickedness which is in the heart, and is wrought there. When Christ teaches, he will show men the deceitfulness and wickedness of their own hearts; he will teach them to humble themselves, and to seek to be cleansed in the Fountain opened for sin and uncleanness.