Plaut noted that the command to observe the Sabbath in preceded the account of the Tabernacle's construction just as it had been commanded at the end of the original instructions in so the Sabbath was the bridge that connected the building of the Tabernacle with its deeper purpose. Professor Nahum Sarna, formerly of Brandeis University, wrote that the injunction to observe the Sabbath in practically repeats verbatim, with an addition not to kindle fire on the Sabbath. The wording of this prohibition led the Rabbis of the Talmud to understand that fire may not be kindled on the Sabbath itself but may be lit before the Sabbath if not refueled on the Sabbath. The Karaites rejected this interpretation and spent the day without lights (although some later adherents did accept the Rabbinic practice). Sarna wrote that it was probably to demonstrate opposition to the early Karaite view that the Rabbis mandated lighting candles on Friday nights, and to that end, the Geonim (the post-Talmudic heads of the Babylonian academies) instituted the recital of a blessing over them.