No distinction is made between biblical Christianity and popish Christianity. The latter purports to have the power to come up with ever new revelation, opening the door for abuses that are not countenanced in the New Testament text itself. (To be fair to the Roman church, the precipitating factor for the Inquisition and Crusades was not Jews but Muslims, although Jews got caught in the midst of the battle and were not always treated with the scriptural deference they deserved.)
A notable New Testament fact is that the Lord’s Day (commemorating the resurrection of Jesus) and the Jewish Sabbath were contemporaneously observed by Christians. The Jewish Sabbath fell into disuse in the Church as Jews pretty much abandoned the Christian church in the centuries after the Temple fell, and it became by default a gentile following. (Seventh-Day Adventists of today are well meaning but do not account correctly for the accommodation to the gentiles in Acts 15, believing that to be only a temporary accommodation.)
It is a sad fact that corruption began in the early church as it lost its roots. As pagans, that worshipped the sun, were incorporated into the church, their day of worship was contemporaneously observe (Sun Day). The truth is Jesus kept the Sabbath as prescribed in the Fourth Commandment. He proclaimed the Sabbath as the Lords Day (Mark 2:28). There is no Biblical commandment to observe Sunday as there is for the sabbath. If we love Jesus He reminds us to keep His Commandments.