..The Sabbath started with the Jewish people ...
No. First of all, the Sabbath begins with "God", JEHOVAH Elohiym, in Genesis 2:1-3; Exodus 20:8-11, as it is His Holy Day, His rest. It was given to Adam, as per Ecclesiastes 12:13-14, so also Mark 2:27-28 (for NT believers). Moses was "Hebrew", of "Levi". Zipporah, wasn't a "Jew", neither the "mixed multitude" that came out of Egypt with the Israelites. There is not a single scripture in OT or NT that states that the sabbath is just for "Jews", or "started wit the Jewish people", not one. It is a myth. Moses was a "sabbath reformer", since in the bondage of Egypt, they had forgotten the sabbath, and so God sends Moses back to reform, in Exodus 5, and we see more reform in Exodus 12-16, before anyone ever reaches Mt. Sinai, Exodus 19-20.
The many times that the "Sabbath" of the LORD is given in the Old Testament (Genesis to Malachi)
Genesis 2:1-3; (see also,
Genesis 18:19, 26:5, &c.)
The sabbath commandment in the beginning with God (Genesis 2:1-3; Exodus 20:8-11; Psalms 119:142).
The sabbath commandment with Adam (Mark 2:27; Ecclesiastes 12:13-14).
The sabbath commandment with Enoch (Genesis 5:22,24; Hebrews 11:5; Isaiah 58:13)
The sabbath commandment with Noah (Genesis 6:9; 2 Peter 2:5; Psalms 119:172).
The sabbath commandment with Eber (Genesis 10:21,24-25; Exodus 3:18, 5:3, 7:16).
The sabbath commandment with Abraham (Genesis 17:9, 18:19, 26:5; 2 Chronicles 20:7; Isaiah 41:8; James 2:23; John 15:14).
The sabbath commandment with Isaac (Genesis 17:9, 18:19, 26:5).
The sabbath commandment with Jacob/Israel (Genesis 17:9, 18:19, 26:5, 32:28).
The sabbath commandment with Moses (Exodus 5:4-5;, 16:1-36, 20:8-11; Deuteronomy 5:12-15, 31:12-18). ...
The sabbath commandment with Jesus (Luke 4:16-19).
The sabbath commandment with the Apostles/Disciples (Acts 1:2, (4:24), 13:14,27,42,44, (14:15), 15:21, 16:13, 17:2, 18:4; Hebrews 3:11,18, 4:1,3,4,5,8,9,10,11; Revelation 1:10, 10:6, 12:17, 14:6-7)
The sabbath commandment with us today (Hebrews 4:9; Revelation 12:17, 14:6-7; John 14:15; Exodus 20:6,8-11).
The sabbath commandment on into eternity (Isaiah 66:23).
Exodus 5:4-5,8-9, 16:23-30, 20:8-11, 23:12, 31:12-18, 34:21, 35:1-3
Leviticus 19:3,30, 23:3,11,15-16,38, 24:8, 26:2
Numbers 15:32, 28:9
Deuteronomy 5:12-15
2 Kings 4:23, 11:5,7,9, 16:18
1 Chronicles 9:32, 23:31
2 Chronicles 2:4, 8:13, 23:4,8, 31:3
Nehemiah 9:6,14, 10:31,33, 13:15-22
Psalms 92:1, 146:6
Isaiah 56:2,4,6, 58:13, 66:23
Jeremiah 17:21-27
Ezekiel 20:12-24, 22:8,26, 23:38, 44:24, 46:1,3-4,12
Amos 8:5
The many times that the "Sabbath" of the LORD is given in the New Testament:
Matthew 12:1,2,5,8,10,11,12, 24:20, 28:1;
Mark 1:21, 2:23,24,27,28, 3:2,4, 6:2, 7:6-9, 15:42, 16:1;
Luke 4:16,31, 6:1,2,5,6,7,9, 13:10,14,15,16, 14:1,3,5, 23:54,56;
John 5:9,10,16,18, 7:22,23, 9:14,16, 12:1 (calculated), 19:31;
Acts 1:2, 13:14,27,42,44, 15:21, 16:13, 17:2, 18:4;
Additional references are:
John 12:1 (six days before the Passover, Jesus was at Lazarus' house, on Sabbath)
Hebrews 3:11, 4:1,3,4,5,8,9,10,11; [Hebrews 4:9 "rest" Greek: sabbatismos, literal sabbath-keeping]
Revelation 1:10 [kuriake hemera, "the Lord's Day" [the 7th Day Sabbath, not "the Day of the Lord", this is totally different in the Greek], see Genesis 2:1-3, Exodus 20:8-11, Deuteronomy 5:12:15, Isaiah 58:13, 66:23, Matthew 12:8, Mark 2:27,28; Luke 6:5 ], Revelation 10:6 [see also Exodus 20:11, 31:17; Nehemiah 9:6; Psalms 146:6; Acts 4:24, 14:15, Revelation 14:7]; Revelation 14:7 [see previous], etc
Additionally, further references in the Greek are [every single 'first [day] of the week' text, as each text clearly shows that the first day is simply a number, with no special association or designation, other than it is simply one day toward the culmination of the week, being the 7th Day the Sabbath of the LORD thy God]:
Genesis 1:5 (Masoretes Hebrew) יום אחד׃ (Transliterated) yôm echäd f
Matthew 28:1(a) - (Koine Greek) οψε δε σαββατων (Transliterated) oye de sabbatwn
Matthew 28:1(b) - (Koine Greek) εις μιαν σαββατων (Transliterated) eiV mian sabbatwn
Mark 16:2 - (Koine Greek) και λιαν πρωι της μιας σαββατων (Transliterated) kai lian prwi ths mias sabbatwn
Mark 16:9 - (Koine Greek) αναστας δε πρωι πρωτη σαββατου (Transliterated) anastas de prwi prwth sabbatou
Luke 24:1 - (Koine Greek) τη δε μια των σαββατων (Transliterated) th de mia twn sabbatwn
John 20:1 - (Koine Greek) τη δε μια των σαββατων (Transliterated) th de mia twn sabbatwn
John 20:19 - (Koine Greek) τη μια των σαββατων (Transliterated) th mia twn sabbatwn
Acts 20:7 - (Koine Greek) εν δε τη μια των σαββατων (Transliterated) en de th mia twn sabbatwn
1 Corinthians 16:2 - (Koine Greek) κατα μιαν σαββατων (Transliterated) kata mian sabbatwn
That the Sabbath [of the Lord thy God], [being] the 7th day, is always the culmination of the week in God's Created order and is always referred to as such in all of scripture.
Therefore, every single “first [day] of the week” text upholds the 7th Day Sabbath, and is undeniable evidence of its continued existence and prominence.
The body of believers may gather on any and every day with no injunction anywhere found in scripture against such, and in truth they met "daily", "continually", etc (Mat 26:55; Mar 14:49; Luk 22:53, 24:33,36; Acts 19:9) and likewise among the followers of Jesus Christ (Luk 24:51,53; Acts 1:3,9, 2:46-47, 5:42, 6:1, 16:5, 17:11,17; Heb 3:13, etc).