Our concern in this note is not the ethics of the transaction but the Hebrew words.
What Esau apparently told Jacob doesn’t sound logical. The impression we get is that he was weary – ayef (Gen. 25:29-30) – and was desperate for soup.
But when people are weary what they need is sleep.
Ibn Ezra has an explanation which most of the translators have not noticed. He links Esau’s words to a passage in Isaiah (32:2) about eretz ay’fah, a parched land. Ayef can mean tired: it can also mean parched and thirsty.
The word appears in this sense in Judges 8:5, where Gideon and his men are famished. Another example is II Sam. 17:29, where the people are hungry, famished and thirsty.
Esau certainly was tired after a long day in the field (according to Rashi, what tired him out was spending the day killing), but his overwhelming emotion was thirstiness.
What he needed was something to drink to alleviate his thirst, and that’s why he needed soup.