Jamieson, Fausset and Brown on Matthew 15:6

6. And honour not his father or his mother, he shall be free--that is, It is true, father--mother--that by giving to thee this, which I now present, thou mightest be profited by me; but I have gifted it to pious uses, and therefore, at whatever cost to thee, I am not now at liberty to alienate any portion of it. "And," it is added in Mark (Mr 7:12), "ye suffer him no more to do aught for his father or his mother." To dedicate property to God is indeed lawful and laudable, but not at the expense of filial duty.

Thus have ye made the commandment of God of none effect--cancelled or nullified it "by your tradition."