Some churches do teach that, but it is not in scripture. The phrase "first day of the week" found in scripture in the Greek is actually "first of Sabbaths", "mia sabbaton". It was actually a particular Sabbath in the Spring of the year. The New covenant is the old covenant Law written on the heart. We have One Bible, One God and One Faith. The Christian religion is the Hebrew religion with a savior who has already fulfilled the Law (what Christ did was prophesied to do).
Some churches do teach that, but it is not in scripture. The phrase "first day of the week" found in scripture in the Greek is actually "first of Sabbaths", "mia sabbaton". It was actually a particular Sabbath in the Spring of the year. The New covenant is the old covenant Law written on the heart. We have One Bible, One God and One Faith. The Christian religion is the Hebrew religion with a savior who has already fulfilled the Law (what Christ did was prophesied to do).