Orthodox Jews all observe the rule of separating milk from meat. But just how long must one wait between eating meat and milk, and what is the source for this?

The Gemara
The Gemara (Chullin 105a) cites R’Chisda, who says if you eat meat, you cannot eat cheese afterwards. However, R’Chisda does not specify how long this prohibition remains in effect. Mar Ukva then says that his father was much stricter than he in keeping this rule and waited twenty-four hours between meat and cheese, but Mar Ukva himself only waited until the next Seudah (meal).

The impression one gets from this statement is that Mar Ukva’s father was being extra strict, while Mar Ukva waited the amount of time he felt was absolutely required according to the halachah. If so, we should decide the halachah based on Mar Ukva’s opinion. This leaves us with the question of how long is the amount of time between one meal and the next?

Positions of the Rishonim
This point is debated by the Rishonim on this Gemara. Rambam (Maachalos Asuros 9:8) says we wait the amount of time one actually waits between meals, which he says is about six hours. Rosh (Chullin 8:5) says similarly that we must wait the normal time between the morning meal and the evening meal. Based on this, the Hagahos Asheri cites Hagahos Maimonios (Maachalos Assuros 9:#3 in) who concludes that we indeed wait six hours in between meat and milk, since this was the amount of time between meals According to Ran, the Rif (Chullin 37b in the pages of the Rif) also takes this position when he says we wait “shiur mai d’tzarich lseudah acharisi,” “the amount of time necessary to wait before beginning another meal,” though others such as Raah are unsure if this is really what the Rif meant. Many other Rishonim hold this way as well, including Rashba (Chullin 105a and Toras HaBayis 86a in old editions; Rashba Toras HaBayis also implies that R’Chisda agreed with Mar Ukva’s father that twenty-four hours is required, interestingly enough), Tur, and Shulchan Aruch (Yoreh Deah 89:1; see Beis Yosef there as well concerning how Rishonim conclude that one must wait the same length of time between meals of chicken and milk as one would wait between meals of beef and milk).

A number of Rishonim interpret the Gemara differently, however: Tosafos (Chullin 105a s.v. lseudasa) understands Mar Ukva to mean that we wait only until you could potentially start a new meal, which just means waiting until after bentching, removing the food table (which was the Talmudic practice similar to “clearing off” tables today), and performing Kinuach and Hadachah (different forms of rinsing the mouth), but not actually waiting until the next official meal of the day some six hours later. According to this, all you have to do is finish your meal completely and then you can eat milk products. Some other Rishonim take this position as well, such as Mordechai, Raaviah and Hagahos Maimonios (cited in the Beis Yosef O.C. 173).

What are the reasons for each opinion? Tosafos might say that all we require is a significant “heker” or method of demonstrating a separation between meat and milk, and finishing the meal and starting a new one qualifies. According to the Rishonim who require six hours, there are two possible explanations: A) Swallowing meat brings out a fatty residue which remains in the throat for a while, perhaps for as long as six hours (this is Rashi’s explanation for R’Chisda, and although he doesn’t mention six hours, it would explain this opinion). B) Six hours allows time for the meat between the teeth to decay (this is Rambam’s approach). There may be some practical differences between the two opinions (e.g. chewing on food for a child and spitting it out – in such a a case, the first explanation wouldn’t apply because you didn’t swallow the food), but Shulchan Aruch (89:1) appears to employ both opinions together.

The Rulings of Shulchan Aruch and Rama
As mentioned, Shulchan Aruch says we wait 6 hours, while Rama quotes the other opinion that just bentching, removing the table, and doing kinuach and hadachah is sufficient. But Rama then says that the accepted custom is to wait one hour, and the question is where this custom developed, since none of the Rishonim mentioned hold this way.

In the Darchei Moshe (89:#1), the Rama himself refers to Hagahos Shaarei Dura (76:2) that reports many made up their own compromise to wait an hour after eating meat, and even though we don’t have a source for this specific length of time, we can’t protest since Tosafos ruled even more leniently and permitted it immediately. Darchei Moshe also cites Issur V'Heter Aroch (40:4-5,7) who mentions this minhag as well (and assumes it was true for chicken as well as meat).

Some attempt to provide precedents for this custom, such as the Vilna Gaon (Beur HaGra 89:6) who cites a Zohar (Parshas Mishpatim) that a person should wait one hour between milk and meat. Others, such as Taz (89:2), assume that it was a custom initiated by the common people who followed Tosafos but wished to add an additional level of precaution to it. A third approach is offered by Kresi Uplesi, who suggests that it is linked to the beginning of the digestive period which may occur about an hour after eating (see Berachos 53b and Rishonim there). He adds that the six-hour approach also links the waiting period to digestion, but whereas the one-hour approach is based on waiting until the beginning of digestion, the six-hour approach requires waiting until the end of digestion.

The problem with this suggestion is that there is no mention of digestion being a relevant factor in determining how long to wait between milk and meat in any of the Rishonim quoted above. In any case, these are some of the explanations given to explain the custom of waiting one hour, and some original Dutch Jews continue to follow this custom today (see R.Binyamin Forst in “The Laws of Kashrus” p.197).

Although Rama does record waiting one hour as the prevalent custom, Rama himself says it is proper to wait 6 hours, and many Acharonim strongly concur, including Shach (89:8), Chochmas Adam (40:13) and Aruch HaShulchan (89:7). Nevertheless, there were some Acharonim, such as Darchei Teshuvah (89:6) who report that the custom among most people was to follow the lenient position of the Rama and wait one hour; only the “medakdekin” (especially careful people) followed Rama’s opinion that it is proper to wait longer, and waited six hours.

The Three-Hour Opinion
There is also one other minority opinion in the poskim that one should wait three hours between meat and milk. This is first mentioned by R’Yerucham (15:31:39) and again by Darchei Teshuvah (89:6) who does not cite R’Yerucham, but instead cites the Mizmor L’Dovid (R.Dovid Prado) that explains that during the winter months in Europe, when the sun sets quite early, the standard amount of time between the lunch and dinner meals was approximately three hours, so even according to the approach that we wait the actual time between meals, we should follow the custom in each locale, and if part of the year this was three hours, we can accept this all the time (see also Pri Chadash here who says one can wait four hours for the same reason, though he says it should depend on the season and how long one actually waits at that time of year).

Contemporary authorities generally advise that unless one has a family custom to wait less, one should follow the opinion of six hours, in accordance with the majority view (see R.Forst p.197). However, there may be room for leniency in certain situations.

Illness
Pischei Teshuvah (89:3), Chochmas Adam (40:13) and Aruch HaShulchan (89:7) state that when one is sick, we can be lenient since for Asheknazim it is only a chumra anyway, and one hour suffices, as per the accepted custom recorded in Rama (Chochmas Adam adds that you need to clean your teeth and bentch first, while Aruch HaShulchan adds you need kinuach and hadachah as well, though see R. Forst who indicates that Kinuach and Hadachah may not be necessary).

Already Made a Berachah on Milk
R. Forst (p.200) cites Beer Moshe (4:24) and Sdei Chemed that to avoid a Berachah L’vatalah (blessing in vain), one can drink a little milk if one hour has passed. Therefore, they allow drinking a small amount of milk if one already recited the berachah for it. R. Ovadia Yosef (Yechaveh Daas 4:41) says it might be allowed even before one hour has passed, the logic being that the real shiur is over right after the Seudah, and waiting one hour was only a custom, so for a potential Berachah Lvatalah (which may be an issur Deoraisa) it should be permitted even if less than an hour has passed (though if we need Kinuach-Hadachah according to Tosafos, perhaps for that reason one shouldn’t drink the milk).