5. The origin of SundayIn the first centuries, Sunday, being made a festival in honor of Christ's resurrection, received attention as a day of religious services and recreation, but seventh-day Sabbath rest (based on the Jewish Shabbat, because the earliest Christians were all Jews) was still observed by "almost all churches". Often first-day worship (Sunday morning or Saturday night) was practiced alongside observance of seventh-day Sabbath rest and was a widespread Christian tradition by the 2nd century, attested in patristic writings of the 2nd century; over time, Sunday thus came to be known as Lord's Day. These early Christians believed that the resurrection and ascension of Christ signals the renewal of creation, making the day on which God accomplished it a day analogous to the first day of creation when God made the light. Some of these writers referred to Sunday as the "eighth day".The 1st-century or 2nd-century Epistle of Barnabas or Pseudo-Barnabas on Is. 1:13 stated "Sabbaths of the present age" were abolished in favor of one millennial seventh-day Sabbath that ushers in the "eighth day" and commencement of a new world. Accordingly, the eighth-day assembly (Saturday night or Sunday morning) marks both the resurrection and the new creation. Thus first-day observance was a common regional practice at that time.By the mid-2nd century, Justin Martyr wrote in his apologies about the cessation of Sabbath observance and the celebration of the first (or eighth) day of the week (not as a day of rest, but as a day for gathering to worship): "We all gather on the day of the sun" (τῇ τοῦ ῾Ηλίου λεγομένη ἡμέρᾳ, recalling both the creation of light and the resurrection). He argued that Sabbath was not kept before Moses, and was only instituted as a sign to Israel and a temporary measure because of Israel's sinfulness, no longer needed after Christ came without sin. Curiously he also draws a parallel between the Israelite practice of circumcision on the eighth day, and the resurrection of Jesus on the "eighth day".10. When did Justin Martyr write about the cessation of Sabbath observance and the celebration of the first (or eighth) day of the week?