He was correct. Sabbath has always been a day of rest and always will be. Sunday is the Lord's Day and is a day of performing our duties to God to gather together and partake of the sacrament, among other things.
Also, one reason there is ambiguity is because when you take the creation account in terms of Days where "a day unto the Lord is as a thousand years unto man" then you have the duration of a single creation cycle being approximately 7 thousand years. However, when going from one creation cycle to another one they actually overlap by one Day. Thus, if you look at time in those terms you have Day 7 being concurrent with Day 1 on the Lord's Creation calendar. So, I don't get too up tight when people refer to Sunday as a Sabbath Day. It all comes out in the wash.
You are not quite correct as the Lords Day nowhere says was Sunday or the first day in scripture, here is a good explanation..
"after the death of the last of the apostles many of the Gentile Christians, who had been converted from paganism, picked up what they were accostomed to and began to observe the pagan Sunday, which corresponded to the first day of the Biblical week. This practice took its rise about the middle of the second century as the church swell its ranks to get more influence for bishop or leader, and the argument invented for it was that it was a fitting way to commemorate theresurrection of the Lord Jesus, although no commandment from Christ or His apostles was adduced in support of the idea.
These pagans or 'converted' Gentile Christians, in need of a name for this new festival, hit upon the idea of calling it “the Lord‟s day” as it was not the Sabbath. Thus we find in both the Greek and the Latin ecclesiastical literature of the latter part of the second century and the centuries following, frequent references to Sunday by this name. None of these writings cite Revelation 1:10 as Biblical authority for calling Sunday “the Lord‟s day.”
John in Revelation was not talking about the first day.
In E.W. Bullinger's Commentary on Revelation, he explains definitively that the "Lord's day" in Revelation 1:10 is not talking about the first day of the week:
'In [Revelation 1:10] we are told that John saw and received this revelation on "the Lord's Day." Leaving the former part of this verse for the present, let us notice the latter expression, "the Lord's Day." 4
The majority of people, being accustomed from their infancy to hear the first day of the week called the Lord's Day, conclude in their own minds that that day is thus called in [Revelation 1:10] because that was the name of it. But the contrary is the fact: the day is so called by us because of this verse.
In the New Testament this day is always called "the first day of the week." (See Matthew 28:1; Mark 16:2 2, 9; Luke 24:1; John 20:1, 19; Acts 20:7; I Corinthians 16:2.). Is it not strange that in this one place a different expression is thought to refer to the same day? And yet, so sure are the commentators that it means Sunday, that some go as far as to say it was "Easter Sunday," and it is for this reason that Revelation 1:10-19 is chosen in the New Lectionary of the Church of England as the 2nd Lesson for Easter Sunday morning.
There is no evidence of any kind that "the first day of the week" was ever called "the Lord's Day" before the Apocalypse was written. That it should be so called afterwards is easily understood, and there can be little doubt that the practice arose from the misinterpretation of these words in [Revelation 1:10]. It is incredible that the earliest use of a term can have a meaning which only subsequent usage makes intelligible.
On the contrary, it ceased to be called by its Scripture name ("the First day of the week"), not because of any advance of Biblical truth or reverence, but because of declension from it. The Greek "Fathers" of the Church were converts from Paganism: and it is not yet sufficiently recognized how much of Pagan rites and ceremonies and expressions they introduced into the Church; and how far Christian ritual was elaborated from and based upon Pagan ritual by the Church of Rome. Especially is this seen in the case of baptism.5
It was these Fathers who, on their conversion, brought the title "Sunday" into the Church from the Pagan terminology which they had been accustomed to use in connection with their Sun-worship.
Justin Martyr (114-165 A.D.) in his second Apology (i.e., his second defense of Christianity), says, 6 in chap. 67. on "The weekly worship of the Christians," - "On the day called SUN-DAY all who live in the country gather together to one place... SUN-DAY is the day on which we all hold our common assembly, because it is the first day on which God, having wrought a change in the darkness and matter, made the world; and Jesus Christ our Savior on the same day rose from the dead. For He was crucified on the day before that of SATURN [i.e., Saturn's day]; and on the day after that of Saturn, which is the day of the SUN, having appeared to his apostles and disciples, He taught them these things, which we have submitted to you also for your consideration."
It is passing strange that if John called the first day of the week "the Lord's Day," we find no trace of the use of such a title until a hundred years later. And that though we do find a change, it is to "Sunday," and not the "the Lord's Day" - a name which has become practically universal.
Some Christians still perpetuate the name of the Lord's Day for Sunday: but it is really the survival of a Pagan name, with a new meaning, derived from a misunderstanding of [Revelation 1:10]."
