Do Protestant writers acknowledge the same?

Answer

They do.
NOTE - "IS there no express commandment for observing the first day of the week as Sabbath,
instead of the seventh day?-None whatever. Neither Christ, nor His apostles, nor the first Christians
celebrated the first day of the week instead of the seventh as the Sabbath."-New York Weekly Tribune,
May 24, 1900.
"The Scriptures nowhere call the first day of the week the Sabbath. . . . There is no Scriptural
authority for so doing, nor of course any Scriptural obligation." The Watchman (Baptist).
"The observance of the first instead of the seventh day rests on the testimony of the church, and
the church alone.' -- Hobart Church News, July 2, 1894.
For additional testimonies, see reading on page 146.

What encouraging statement follows concerning the supply of power to the faint?
What is felt in heaven when a sinner repents?
What prophecy of Isaiah was fulfilled at Christ's birth?
What is to be the fate of those who, instead of worshipping God, engage in this false worship?
Why are they demanded now?
For whose sake did Christ say the period of papal persecution would be shortened?
How are the people described who are developed by the threefold message here referred to?

Questions & Answers are from the book Bible Readings for the Home Circle