What is you source for this document and did you insert the stuff in the [brackets]? At any rate, the author still confessed "not acceptable to me" and "that which I have made". It is clear that his argument is from the position of himself and NOT from the position of "Thus saith the LORD".
If you actually read the source document, and not just some Seventh-Day Adventist pull-quote, you would have seen that the context was an exegesis of Old Testament passages indicating the supercession of the Sabbath. He explicitly was referencing Divine quotations.
Moreover concerning the Sabbath likewise it is written in the Ten Words, in which He spake to Moses face to face on Mount Sinai; And ye shall hallow the Sabbath of the Lord with pure hands and with a pure heart.
And in another place He saith; If my sons observe the Sabbath then I will bestow My mercy upon them.
Of the Sabbath He speaketh in the beginning of the creation; And God made the works of His hands in six days, and He ended on the seventh day, and rested on it, and He hallowed it.
Give heed, children, what this meaneth; He ended in six days. He meaneth this, that in six thousand years the Lord shall bring all things to an end; for the day with Him signifyeth a thousand years; and this He himself beareth me witness, saying; Behold, the day of the Lord shall be as a thousand years. Therefore, children, in six days, that is in six thousand years, everything shall come to an end.
And He rested on the seventh day. this He meaneth; when His Son shall come, and shall abolish the time of the Lawless One, and shall judge the ungodly, and shall change the sun and the moon and the stars, then shall he truly rest on the seventh day.
Yea and furthermore He saith; Thou shalt hallow it with pure hands and with a pure heart. If therefore a man is able now to hallow the day which God hallowed, though he be pure in heart, we have gone utterly astray.
But if after all then and not till then shall we truly rest and hallow it, when we shall ourselves be able to do so after being justified and receiving the promise, when iniquity is no more and all things have been made new by the Lord, we shall be able to hallow it then, because we ourselves shall have been hallowed first.
Finally He saith to them; Your new moons and your Sabbaths I cannot away with. Ye see what is His meaning ; it is not your present Sabbaths that are acceptable [unto Me], but the Sabbath which I have made, in the which, when I have set all things at rest, I will make the beginning of the eighth day which is the beginning of another world.
Wherefore also we keep the eighth day for rejoicing, in the which also Jesus rose from the dead, and having been manifested ascended into the heavens.-- Epistle of Barnabas, XV.i-xv (Lightfoot translation).
The Church very early on had all-but-ceased engaging in Sabbatarian worship. Such is the invertible conclusion of any fair-minded historian.
Read it for yourself to see if you can come to a different interpretation.