John Gill Commentary Mark 7:9

"And he said unto them, Full well do ye reject the commandment of God, that ye may keep your tradition." — Mark 7:9 (ASV)

And he said to them

He continued his discourse, saying,

full well,

or "fairly",

you reject the commandment of God, that you may keep your own
tradition:

These words may be considered as spoken ironically, thus: as pious and excellently good men, you in a very fair and handsome manner, reject and make void the commandments and laws of God; and it is very fit it should be so, in order to preserve your own traditions, that nothing may be wanting to keep up the honour of them, and a due regard to them.

The Arabic version reads the words by way of interrogation, "is it fit that you should omit the commandments of God, and keep your own statutes?" and so the Ethiopic, "do you rightly make void the commandment of God, that you may keep your own commandment?" Which makes them come nearer to the passage in Matthew; (See Gill on Matthew 15:3).