Question
What is the difference between,
Ἐν δὲ τῇ μιᾷ τῶν σαββάτων
in Acts 20:7 and
κατὰ μίαν σαββάτου
in 1 Corinthians 16:2?
Response
The general answer to this question about the difference between the 2 Sunday expressions is that although there are many grammatical and vocabulary differences, there is only one semantic difference. The sabbath is originally the day of rest, but since it occurred every seventh day according to the Mosaic calendar, it also refers to the week by extension. The ancients could see 7 movable heavenly bodies that moved relative to the fixed rotation of the starry background. μιᾷ is dative since Ἐν governs the dative. It is feminine singular since it refers to the feminine singular noun ἡμέρᾳ. Greek is more elliptical than English. The same goes for accusative μίαν. Since σαββάτου is a time word referring to a day, the author does not need to add ἡμέρᾳ explicitly because association plays a big role in communication and the adjective can stand for the noun.
μιᾷ is a cardinal number referring to day 1, but is understood as ordinal as in Genesis, the first day of the week or the first day after the sabbath. The use of the plural/singular distinction is usually important in the GNT as in English, but at other times, particularly referring to time, it is flexible as with σαββάτων/σαββάτου where singular σαββάτου refers to any of many weeks and plural σαββάτων refers to a particular day. It is the writer’s option. Unlike σαββάτων/σαββάτου, μιᾷ/μίαν needs to be singular in each of the 2 expressions.
The use of the article in prepositional phrases is also optional. However, the canon of Apollonius is usually observed. If μιᾷ is articular, so is σαββάτων. Otherwise, both are anarthrous. The student can see that the Greek speaker/writer had many options available that were equivalents and did not alter the semantics. Some exegetes make the mistake of assuming that different constructions must always express different meanings. Similarly, the translator into an idiomatic target language has many options while preserving the meaning, hence the many translations, often all correct. In contrast, the prepositions were usually determined by the writer’s purpose and affected the reader’s understanding.
In classical Greek prepositions were less common, and case was more often used to make semantic distinctions. Koine often used case and preposition both redundantly for clarity. Sometimes the Koine authors also left the prepositions off without altering the meaning. Of the 3 oblique cases, genitive refers to the point from, dative refers to the point at, and accusative refers to duration or repetition if used with a preposition.
So Acts 20:7, referring to a particular day when Paul was passing by, naturally expresses this point in time with dative and a dative preposition of time. And 1 Corinthians 16:2, referring to a repeated practice, naturally expresses the idea of each Sunday or every Sunday with κατὰ μίαν because καθ’ ἡμέραν is the Koine idiom for every day. This was such a catchy idiom that it passed through Latin to Spanish and French cada dia, chaqu’un.
The Sabbath was sacred in the Law of Moses and led to many disputes between Jesus and the Pharisees over works and the letter and spirit of the law. The change of the day of worship from the sabbath to Sunday by the Christians of the New Covenant is hotly disputed by the Seventh Day Adventists. They pretend to know history and claim that Constantine changed the worship day in violation of sola scriptura and that the other Protestants are all guilty of hypocrisy.
The Seventh Day Adventists get their history from their imagination. The instructions for Sunday worship is in the Didache 200 years before Constantine which was a manual for the churches while the Apostle John was still alive. The original Church before the Reformation never subscribed to sola scriptura and believes that as the keepers of the New Covenant they had the same power that the Jerusalem council had in Acts 15 to override the Mosaic law from the Old Covenant. The Orthodox teach that the change occurred on Thomas Sunday before the Ascension when Thomas confessed Jesus as Lord and God.
The expression the Lord’s Day μιᾷ σαββάτων for Sunday occurs in Matthew 28:1, Mark 16:2, Luke 24:1, John 20:1, all between the resurrection and the ascension, Acts 20:7 and 1 Corinthians 16:2, all as objects of prepositions. The other Protestants who espouse sola scripture sometimes claim that these mentions of the first day actually authorize the worship day change biblically somehow. Sunday was not part of Christ’s pre-crucification doctrine. The equivalent expression, the Lord’s Day ἐν τῇ κυριακῇ ἡμέρᾳ was used once in Revelation 1:10. To this day it is the expression for Sunday in Greek and by extension in many European languages.
Calendars identified dates, not days; there were many ancient calendars. Most modern scholars appear to believe that the 7 day week with the 7 named days did not much predate Christ outside Judea and Babylon, in spite of the fact that the days are named after the 5 planets and sun and moon, which were known in ancient times. The word week often occurs throughout the OT, but not the day names, which are now adopted throughout the world.