Halachos of Coffee

In his treatise, HaKafe v'haMitzvot, R. Aaron Schuman writes: It was 
revealed at Mount Sinai that Hashem ordained that heat shall flow from 
hotter regions to colder. This revelation was preserved as a secret 
teaching until R Josiah Gibbowitz (z"l) inscribed it as Hashem's 2nd 
Commandment of Thermodynamics. There is a little known mitzvah, "Thou 
shalt never stir the cream into thy morning coffee; thereby shall you 
observe convection currents and remember My second commandment of 
thermodynamics." (Since this is a time-bound mitzvah, women are exempt.) 
The parenthetical remark seemed incorrect, a little further research 
uncovers a rich tradition of Jewish law brewing around this allegedly 
"secret teaching."

Even if we understand that this mitzvah only applies to coffee drunk in 
the morning, women are only exempt from mitzvot aseh shehazman grama
[time-bound commandments phrased as "thou shalt"], whereas this is a
mitzvat lo taaseh [phrased as "thou shalt not"]. Therefore we conclude 
that women are equally bound to contemplate convection currents. R. Chama 
bar Karkar argues that this mitzvah is not really time-bound at all.

What if one only drinks coffee after supper? The mitzvah applies to kos 
rishon (the first cup of coffee in each day), whether drunk in the 
morning, afternoon or evening. Some delay drinking kos rishon until later 
in the day, when they have more time to observe the swirling patterns at 
greater length. Do we not pray in the Amida: "v tovotecha shebehol eyt, 
erev vavoker vatzohoraim" [(we thank you...) for your goodness at all 
times evening, morning and afternoon]? And is not coffee with cream one of 
G-d's goodnesses? Therefore our sages maintain that this mitzvah applies 
to coffee drunk at any time, not only kos rishon. (Halacha follows this 
opinion.) Once again, women and men are both  obligated in this mitzvah. 
Are Jews, then, commanded to drink coffee? No, but those who do are 
considered praiseworthy. What of those who do not drink coffee? They are 
obligated to contemplate the coffee of a friend, and to refrain from 
stirring it (masechet Shotah, perek Shtayim Shotim B'kos, mishnah kaf-he).

May one contemplate the coffee of a non-Jew? Rambam notes that coffee has
never been used in avodah zarah [idol worship], so one may contemplate it.
The RiTzPa notes that one may not drink it unless it was prepared and 
served in kosher vessels, but one may contemplate it even in unkosher 
vessels. Later commentators note that Ashkenazim do not do this, and 
Sephardim only do it when it will annoy Ashkenazim.

May one prepare the coffee, refrain from stirring, yet not drink? Bet 
Hillel say that such a person is yotze, as long as one observes the 
convection currents and remembers the 2nd Commandment of Thermodynamics.  
Bet Shammai say that one must drink as well. (As usual, we follow Bet 
Hillel.) Rashi comments that although one need not drink the coffee, the 
coffee must not be wasted, lest we transgress bal tashchit [do not 

What of coffee drunk following a meat meal? Since real cream is forbidden 
in this circumstance, may one observe the mitzvah with pareve ersatz 
cream? Rambam says no, since the principle of hiddur mitzvah [beautifying 
a commandment] demands that we use the tastiest ingredients we can afford, 
and mocha mix is inferior to authentic cream. Hence we do not serve coffee 
after meat. (Black coffee does not fulfill the mizvah.) Mishnah Brewrah 
notes that those who are especially pious refrain from eating meat at any 
time so that they will always be ready to observe this mitzvah with real 
cream. So important is real cream that even skim milk is unacceptable 
(except for those with certain medical conditions). Concerning hiddur 
mitzvah, the Kos Tam (R. Yuban Chockfullanussen) argues that in addition 
to fine quality coffee and cream, one must also use fine implements. Not 
only must the coffee be served in a delicate cup (with a saucer!), but 
when one refrains from stirring, one must refrain from stirring with a 
silver spoon. To refrain with a wooden or plastic stick, when a fine spoon 
was available, shows disrespect for the Torah and brings disgrace on one's 

One should take care to avoid spilling any coffee on the unused stirring
implement, so that nobody will see it and conclude (erroneously) that 
stirring is permissible. Likewise, although one may first stir sugar into 
coffee and then refrain from stirring after adding cream, those who are 
strict do not do this, to avoid wetting the stirrer. Neither may one stir 
the coffee first, and then pour in cream while the coffee is still in 
motion relying on turbulence to mix the cream. The Torah is explicit that 
the purpose is to observe convection currents (which must be generated by 
temperature diffential, and not any other motion or current). In recent 
years it has become common to use special coffee cups made of glass, so 
that one may observe the currents not only from the top, but from the 
sides and bottom as well. Harei zeh mishubach, although we do not 
invalidate cups made of fine china.

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