Revelation 1:10, The Lord’s Day. This verse is one of the cliche biblical passages that mainstream church scholars use to “prove” Sunday’s replacement of the Sabbath. The problem with this position is that there’s no clear scriptural proof that the apostles ever changed the Sabbath to Sunday. What’s more, to view this passage as referring to Sunday is to take a phrase the early church fathers used as a euphemism for Sunday when pushing for Sunday in place of Sabbath observance and to retroactively apply this meaning to John’s use of the phrase. Frankly, it is biased and dishonest scholarship to take the phrase “the Lord’s day” with its second century colloquial meaning and then to back-apply this meaning to John’s use of the phrase when there’s no reason to believe this was John’s intended meaning.
Alternatively, the phrase, “the Lord’s day, can be a reference to the biblical term “the day of the Lord’s wrath” when YHVH, in the end times, will judge the nations for their wickedness. This is a point that several biblical scholars have made (see From Sabbath to Sunday, by Samuele Bacchiochi, p. 111; E. W. Bullinger’s Companion Bible footnote on Rev 1:10; The Jewish New Testament Commentary on this verse, p. 791, by David Sterns).
There is actually more scriptural proof that the phrase “the day of the Lord” is a reference to the seventh day Sabbath than to the first the week. In Isaiah 58:13, the prophet YHVH refers to the Sabbath as “my holy day…the holy day of the Lord.” So conceivably, it could have been on the Sabbath day itself that John received his vision on the island of Patmos about that great and terrible day of YHVH’s wrath that is to come on the earth just prior to the Messiah’s second coming.