He took cream and milk and the calves that he had prepared, and he placed [them] in front of [the angels], and he was standing over them under the tree, and they ate.
-- Breshis 18:8
Classic Questions
How could Avraham serve milk and meat together? (v. 8)
Da'as Zekeinim: Rashi writes that Avraham served them "bit by bit, as each item was prepared" (v. 8). Thus, he did not serve them meat and milk together, which is forbidden, but rather milk, and then afterwards meat ("cream and milk, and the calves"), which is permissible.
The Rebbe's Teachings
Milk & Meat (v. 8)
In addition to the argument of Da'as Zekeinim that the cream and calves were served separately, thus circumventing the prohibition of eating milk and meat, one could also argue that he offered each of the angels either milk or meat. Thus, "three calves' tongues with mustard" were prepared (Rashi, v. 7) to give each of the guests the option of eating meat. This was done in order to fulfill the mitzvah of welcoming guests in the best possible fashion. No guest, however, was served milk and meat.
(Based on Likutei Sichos vol. 6, p. 150)
All 3 times in Torah where it refers to separating meat and milk a temperature is involved.
There is no question from Torah that milk and meat cannot be heated together - eg stroganoff, pizza, lasagne, (many Italian recipes it seems), grilled sandwiches, etc but it certainly appears to me that Abraham did keep Kashrut by serving milk and meat at the same meal - eg a meat main course and yogurt dessert.
However it was done, they were served as separate items and certainly not 'heated together'. As it was an extremely very hot day perhaps both milk and meat were served cold at the meal. A plain and simple reading of Torah shows this would not break the Torah prohibition (but would the Rabbinical - which could be wrong). 3 times the temperatures are very specific (doesn't include melting - for instance, a sandwich of bread, butter, and cooked meat sitting in the sun).
This is an issue that I have pondered for years and no one has ever explained it. Comments appreciated please
Our sages teach that the forefathers observed every aspect of Jewish Law, even including those laws established by the sages, they give an example of Eruv Tavshilin, done to allow us to cook on Friday which is Yom Tov for Shabbat - which is a Rabbinic enactment.
I guess the question is then, why did the sages establish a law prohibiting meat and milk at such times as one or both are cold? (Which therefore is contrary to the teaching of Torah). Were they somehow not enlightened to the fact that there is a temperature involved? I don't hear of the temperature (and I have never seen a study where it is particularly addressed).
I agree that the forefathers observed every aspect of Jewish Law - which only serves to support my analogy. A good example is the fact that Noach took more clean than unclean animals and creatures into the ark. There is nothing in Torah to indicate to Noach which is clean or unclean; he 'knew'.
Similarly, just 3 days before Abraham had served the milk (+ butter) and meat together, G-o-d told Abram to walk before Him and be perfect. This very fact that Abraham was now perfect just doesn't support a prohibition of serving milk and meat together (other than one based on both heated together- & that was not served.)