John Calvin on Matthew 15:7-8

7. Well hath Isaiah prophesied concerning you. Our Lord now proceeds farther; for he decides on the question in hand, which he divides into two clauses. The first is, that they relied on outward ceremonies alone, and set no value on true holiness, which consists in sincere uprightness of heart; and the second is, that they worshipped God in a wrong way, according to their own fancy. Now though his reproof of pretended and hypocritical holiness appears hitherto to be restricted to persons, yet it includes the substance of this doctrine, from which the full conclusion was, first, that the worship of God is spiritual, and does not consist in the sprinkling of water, or in any other ceremony; and, secondly, that there is no reasonable worship of God but what is directed by the rule of his word. Although Isaiah (29:13) did not prophesy for futurity alone, but had regard to the men of his own age, yet Christ says that this prediction relates to the Pharisees and scribes, because they resemble those ancient hypocrites with whom the prophet had to contend. Christ does not quote that passage exactly as it stands; but the prophet expressly mentions two offenses by which the Jews provoked against themselves the divine vengeance. With their lips only, and by an outward profession, they made a pretense of godliness; and, next, they turned aside to modes of worship invented by men. First, then, it is wicked hypocrisy, when the honor which men render to God is only in outward appearance; for to approach to God with the mouth, and to honor him with the lips, would not be in itself evil, provided that the heart went before. The substance of what our Lord states on this subject is, that, since the worship of God is spiritual, and as nothing pleases him that is not accompanied by the inward sincerity of the heart, they who make holiness to consist in outward display are hypocrites.