Halakhah for Shabbat 50:2
ואיבעית אימא קדש חמור שכן ענוש כרת רב נחמן בר יצחק אמר אמר קרא (דברים יח, ד) תתן לו לו ולא לאורו מכלל דבת אורו הוא:
hence it can be used for light [if defiled].<span class="x" onmousemove="('comment',' For otherwise, why exclude it? ');"><sup>4</sup></span> R. ISHMAEL SAID etc. What is the reason? — Rabbah answered, Since it is malodorous, it is feared that he [the occupant of the house] will leave it and go out. Said Abaye to him, Then let him leave it! I maintain, he replied, that the kindling of the lamp on the Sabbath is a duty,<span class="x" onmousemove="('comment',' I.e., the lamp must be lit where the evening repast is consumed. If the person leaves it and dines elsewhere he does not fulfil his obligation. ');"><sup>5</sup></span> for R. Nahman b. R. Zabda-others state, R. Nahman b. Raba-said in Rab's name: The kindling of the lamp for the Sabbath is a duty; the washing of the hands and the feet in warm water on the eve [of the Sabbath] is voluntary. Whilst I maintain that it is a mizwah.<span class="x" onmousemove="('comment',' Mizwah denotes either a definite precept or something which while not actually commanded is meritorious. The latter is meant here. ');"><sup>6</sup></span>