It’s also written, the very same admonishment, in Deuteronomy, at the end of Torah.
He means it.
Of course, He means it. That's why these man made "traditions" are so dangerous. They corrupt the meaning and message that God has sent. I guess I shouldn't waste my time with the Catholic posters here but I wish they could see that their Church has made a simple service into a complicated legalistic formality it was never meant to be. We are supposed to worship God. It's not complicated.