Catholic tradition refers
to Sunday as the Lord’s Day. The only reference of the Lord’s Day in scripture
is in Revelation 1:10, “I was in the Spirit on the Lord's
day….” Let us see, according to Scripture, which day is defined as the
Lord’s Day: “For the Son of man is Lord even of the
sabbath day.” Matthew 12:8. Seeing that the Lord’s Day is the Sabbath
day, let us again look to scripture to see which day is the Sabbath day: “But the seventh day is the sabbath of the LORD thy God.”
Exodus 20:10.
In any thesaurus, Saturday is
defined as the seventh day of the week, yet some people affirm that Sunday is
the seventh day of the week. Historical evidence clarifies this. Throughout the
ancient languages in addition to modern languages, the seventh day of the week
is referred to as the Sabbath Day. For example in some ancient languages
(including Modern Arabic) Arabic the days of the week are named according to
their numbers, with the word for Sunday meaning one, the word for Monday
meaning two, Tuesday, three, and so on.
In His word, the all-knowing God clearly differentiated the Sabbath day from the first day of the week, and never uses both terms simultaneously to refer to the same day. Acts 13: 42, 44, 16:3, 17:2, 18:4 refer to the Sabbath day (Saturday); Acts 20:7, 1 Corinthians 16:2 refer to the first day of the week (Sunday).

