Kindling any type of fire on Shabbat is forbidden, and doing so constitutes the av melachah of mav'ir.1 Making a fire last longer by fanning it or adding more fuel is also included in the melachah.2 Driving a car, flying an airplane, or turning on an oven, which operate by burning fuel, are all clear examples of mav'ir.

In contrast to the general rule that one is only liable for a forbidden act on Shabbat if it is done in a meaningful quantity, one transgresses the melachah of mav'ir by creating any fire at all, no matter how small.

What is the proper definition of mav’ir? Does it refer to producing heat and light with a flame, or is it consuming something with fire to create heat and light? Why does it matter? One practical difference would be how to categorize the prohibition against using incandescent light bulbs. An incandescent bulb essentially consists of a wire that glows due to resistance to the electric current flowing through it. If we understand that mav’ir constitutes specifically producing heat through the process of combustion, then incandescent bulbs might not be included in the melachah (although still forbidden for other reasons3). If, however, we interpret mav’ir as producing heat and light through fire, then an incandescent bulb, which achieves the same effect, would be included.

Let’s see how some of the great halachic authorities addressed this question.

At the start of his discussion on mav'ir, Maimonides4 writes that one is only liable for kindling a fire if the resulting ash is of use. Otherwise, he argues, it would be considered a purely destructive act for which one is not liable on Shabbat. It would seem from this ruling that Maimonides understands mav'ir to mean creating fire through the process of combustion, and therefore, the result of the combustion itself must itself be useful, not just the light and heat that it emits.

Further on, however, Maimonides implies the opposite. He writes that one who heats iron in order to strengthen it by subsequently submerging it in water is liable for performing a derivative of mav'ir. When metal is heated, nothing is consumed, and yet Maimonides still considers it part of mav'ir.5

In his Shulchan Aruch,6 the Alter Rebbe writes that mav'ir is not about what is being consumed, but about the light and heat it produces. He understands Maimonides to follow this view as well.78

Most rabbinic authorities say that causing a filament to glow by turning on an electric appliance is an act of mav'ir (kindling), and turning the appliance off is an act of mechabeh.9 Incandescent bulbs and toaster ovens are classic examples. Turning on or off other electric appliances, including the use of fluorescent lights or LEDs, is also forbidden on Shabbat, but mav'ir is not a factor because no form of fire is created.

Using Candlelight on Shabbat

Before the advent of electricity, oil lamps were widely used. Out of concern that one may tilt a lamp on Shabbat to make it glow brighter, a clear violation of mav'ir, the Sages prohibited performing any meticulous tasks by such light.10 This prohibition still stands today, and in the event of a power outage, one may not read by the light of Shabbat lamps that burn from oil. There is more room to be lenient with wax candles, because their light is steadier, and tilting them won’t make the candle brighter.11

Mav'ir in the Mishkan

Firewood was burned to heat the vats used to make dyes for the drapes used in the Mishkan.12

Common Activities to Avoid

  • Turning on or raising the flame on a gas stove.
  • Turning on the hot water faucet.
  • Turning up the thermostat on a heating system.