Talmud zu Bereschit 18:1

Rebbi Yehudah¹⁷This paragraph is found also in the Babli (27a) and in both Mekhiltot (to Ex. 17:21). The second paragraph which connects the derivation to the previous association with sacrifices, and hence, with prayer, is found only in the Yerushalmi. learned from words of the Torah, since Rebbi Ismael stated: (Ex. 17:21) “The sun was hot and it melted,” four hours into the day. You say four hours or should it be six hours? When it says (Gen. 18:1): “In the heat of the day”, that means at six hours. Therefore, how can I interpret: “The sun was hot and it melted,” four hours into the day¹⁸Here and in the next paragraph, one supposes, as in most Talmudic derivations, that the vocabulary of the Torah is uniquely fixed and that different expressions must have different meanings. [The only Bible translation that can be clearly dated to Tannaïtic times, the fragments of Aquilas’s Greek translation from the school of Rebbis Eliezer and Joshua, systematically has one-on-one correspondence between Hebrew and Greek words.]! You derive it from (Ex. 17:21): “In the morning,” (Num. 28:4) “in the morning.” Since the first “morning” meant “four hours”, “morning” mentioned there also means “four hours.” At four hours the sun is warm and the shadow is cool. At six hours both sun and shadow are hot. Rebbi Tanḥuma said (Gen. 18:1): “In the heat of the day”, at an hour when there is no shadow for any creature.