The word Shabbat derives from the Hebrew root ש־ב־ת. Although frequently translated as "rest" (noun or verb), another accurate translation is "ceasing [from work]." The notion of active cessation from labour is also regarded as more consistent with an omnipotent God's activity on the seventh day of creation according to Genesis.

A cognate Babylonian Sapattu or Sabattu is reconstructed from the lost fifth Enūma Eliš creation account, which is read as: "[Sa]bbatu shalt thou then encounter, mid[month]ly". It is regarded as a form of Sumerian sa-bat ("mid-rest"), rendered in Akkadian as um nuh libbi ("day of mid-repose").

Connection to Sabbath observance has been suggested in the designation of the seventh, fourteenth, nineteenth, twenty-first and twenty-eight days of a lunar month in an Assyrian religious calendar as a 'holy day', also called 'evil days' (meaning "unsuitable" for prohibited activities). The prohibitions on these days, spaced seven days apart (except the nineteenth), include abstaining from chariot riding, and the avoidance of eating meat by the King. On these days officials were prohibited from various activities and common men were forbidden to "make a wish", and at least the 28th was known as a "rest-day".

The Universal Jewish Encyclopedia advanced a theory of Assyriologists like Friedrich Delitzsch (and of Marcello Craveri) that Shabbat originally arose from the lunar cycle in the Babylonian calendar containing four weeks ending in a Sabbath, plus one or two additional unreckoned days per month. The difficulties of this theory include reconciling the differences between an unbroken week and a lunar week, and explaining the absence of texts naming the lunar week as Sabbath in any language.
Seventh-day Shabbat did not originate with the Egyptians, to whom it was unknown; and other origin theories based on the day of Saturn, or on the planets generally, have also been abandoned.
Sabbath is given special status as a holy day at the very beginning of the Torah in Genesis 2:1-3. It is first commanded after The Exodus from Egypt, in Exodus 16:26 (relating to the cessation of manna) and in Exodus 16:29 (relating to the distance one may travel by foot on the Sabbath), as also in Exodus 20:8-11 (as one of the Ten Commandments). Sabbath is commanded and commended many more times in the Torah and Tanakh; double the normal number of animal sacrifices are to be offered on the day. Sabbath is also described by the prophets Isaiah, Jeremiah, Ezekiel, Hosea, Amos, and Nehemiah.

The longstanding Jewish position is that unbroken seventh-day Shabbat originated among the Jewish people, as their first and most sacred institution. The origins of Shabbat and a seven-day week are not clear to scholars; the Mosaic tradition claims an origin from the Genesis creation narrative.

The first non-Biblical reference to Sabbath is in an ostracon found in excavations at Mesad Hashavyahu, which has been dated to approximately 630 BCE.

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The Tanakh and siddur describe Shabbat as having three purposes:
199 To commemorate God's creation of the universe, on the seventh day of which God rested from (or ceased) his work;
299 To commemorate the Israelites' Exodus and redemption from slavery in ancient Egypt;
399 As a "taste" of Olam Haba (the Messianic Age).
Judaism accords Shabbat the status of a joyous holy day. In many ways, Jewish law gives Shabbat the status of being the most important holy day in the Hebrew calendar:
• It is the first holy day mentioned in the Bible, and God was the first to observe it with the cessation of creation (Genesis 2:1–3).
• Jewish liturgy treats Shabbat as a "bride" and "queen" (see Shekhinah); some sources described it as a "king".
• The Sefer Torah is read during the Torah reading which is part of the Shabbat morning services, with a longer reading than during the week. The Torah is read over a yearly cycle of 54 parashioth, one for each Shabbat (sometimes they are doubled). On Shabbat, the reading is divided into seven sections, more than on any other holy day, including Yom Kippur. Then, the Haftarah reading from the Hebrew prophets is read.
• A tradition states that the Jewish Messiah will come if every Jew properly observes two consecutive Shabbatoth.
• The punishment in ancient times for desecrating Shabbat (stoning) is the most severe punishment in Jewish law. In addition, the divine punishment for desecrating Shabbat, kareth (spiritual excommunication), is the most severe of divine punishments in Judaism.
• On Shabbat an offering of two lambs was brought in the temple in Jerusalem.