Hi Indigo nice to meet you. According to the scriptures, you do not need to go outside of the bible to know what day "the Lords day" is. The Lords day is clearly defined in the bible.
The term "the Lord's day" was used by some in the early Church as a reference to Sunday worship in celebration of the resurrection of Jesus. It comes from a scripture in the bible found in Revelation 1
- REVELATION 1:10 10, I was in the Spirit on the Lord's day, and heard behind me a great voice, as of a trumpet
The Greek words used for the day that JOHN was in the Spirit of is the for Lord's day are
- REVELATION 1:10 εγενομην εν πνευματι εν τη κυριακη ημερα και ηκουσα οπισω μου φωνην μεγαλην ως σαλπιγγος
The word "κυριακη" (translit. "kuriake") is an Adjective - Dative - Singular - Feminine. This means it is being used as a 'possessive' as ownership or belonging to ("of", see 1 Corinthians 11:20
, "the Lord's supper"), which means the "day" in context belongs to "the Lord". It is literally "the Lord's (belonging to) day". This means, that the "day" in context is uniquely "the Lord's" out of all the 7 days of the week, for the day under consideration is that which exists within the week, as a day which repeats weekly. This is extremely important, as those who incorrectly assume it to mean "the first [day] of the week" in lieu of Jesus' resurrection, cannot get a weekly occurrence out of a one-time event, in fulfillment of typology of the Firstfruit/Wavesheaf in Leviticus 23:9-14
, as made known in 1 Corinthians 15:20
The problem here however is that there is not a single scripture that references Sunday or the first day of the week (bible names for the days of the week) to being "the Lords day" in scripture.
According to the scripture "the Lords day" however can be referenced to "the Sabbath day" of Gods' 4th commandment found in Exodus 20:8-11
Letting the scriptures answer this question
- WHAT DAY IS THE LORD'S DAY ACCORDING TO THE SCRIPTURES?
- MATTHEW 12:8 FOR THE SON OF MAN IS LORD EVEN OF THE SABBATH DAY
This then promotes a bit of a dilemma for the Church as there is not a single scripture in all of the bible that days "the Lords day" from Revelation 1:10
is Sunday. Yet there is many scriptures referencing "the Lords day" or Gods' specific claims to ownership of any particular day to the Sabbath day that he blessed and set aside as a holy day of rest for a memorial of creation (see Genesis 2:1-3
) and made one of Gods' 10 commandments (Exodus 20:8-11
God's "ownership" of the Sabbath day or "Lord's day is also repeated elsewhere as "MY" (ownership of the day as in the Greek used in REVELATION 1:10
κυριακη). Other scriptures in the bible pointing to "the Lords day" as being the Sabbath day...
- MATTHEW 12:8 FOR THE SON OF MAN IS LORD EVEN OF THE SABBATH DAY. (the Sabbath day is Lord's day)
- ISAIAH 58:13-14 , If you turn away your foot from the SABBATH, from doing your pleasure on MY HOLY DAY (God's claim to ownership of the Sabbath day); and call the sabbath a delight, the holy of the LORD, honorable; and shall honor him, not doing your own ways, nor finding your own pleasure, nor speaking your own words: , Then shall you delight yourself in the LORD; and I will cause you to ride on the high places of the earth, and feed you with the heritage of Jacob your father: for the mouth of the LORD has spoken it.
- LEVITICUS 19:30 You shall keep MY SABBATHS, (God's claim to ownership of the Sabbath day)and reverence my sanctuary: I am the LORD.
- EZEKIEL 20:12 Moreover also I gave them MY SABBATHS, (God's claim to ownership of the Sabbath day) to be a sign between me and them, that they might know that I am the LORD that sanctify them.
κυριακῇ ἡμέρᾳ used in Revelations 1:10 is in reference to the Lord's ownership of the day. It does not say that this day is in reference to μιά των σαββάτων which means the FIRST DAY OF THE WEEK.
Your challenge here in this OP is to prove from the scriptures alone that the Lord's DAY is in reference to the First day of the week. If you cannot all you have is a teaching and tradition of men that is not supported in the scriptures. There is not a single scripture in all the bible that refers to Sunday as being "the Lords day".