A mess of pottage is something immediately attractive but of little value taken foolishly and carelessly in exchange for something more distant and perhaps less tangible but immensely more valuable. The phrase alludes to Esau's sale of his birthright for a meal ("mess") of lentil stew ("pottage") in Genesis 25:29-34 and connotes shortsightedness and misplaced priorities.
The mess of pottage motif is a common theme in art, appearing for example in Mattia Bortoloni's Esau selling his birthright (1716) and Mattias Stomer's painting of the same title (ca. 1640).
Although this phrase is often used to describe or allude to Esau's bargain, the phrase itself does not appear in the text of any English version of Genesis. Its first attested use, already associated with Esau's bargain, is in the English summary of one of John Capgrave's sermons, c1452, "[Jacob] supplanted his broþir, bying his fader blessing for a mese of potage." In the sixteenth century it continues its association with Esau, appearing in Bonde's Pylgrimage of Perfection (1526) and in the English versions of two influential works by Erasmus, the Enchiridion (1533) and the Paraphrase upon the New Testament (1548): "th'enherytaunce of the elder brother solde for a messe of potage". It can be found here and there throughout the sixteenth century, e.g. in Johan Carion's Thre bokes of cronicles (1550) and at least three times in Roger Edgeworth's collected sermons (1557). Within the tradition of English Biblical translations, it appears first in the summary at the beginning of chapter 25 of the Book of Genesis in the so-called Matthew Bible of 1537 (in this section otherwise a reprint of the Pentateuch translation of William Tyndale), "Esau selleth his byrthright for a messe of potage"; thence in the 1539 Great Bible and in the Geneva Bible published by English Protestants in Geneva in 1560. According to the OED, Coverdale (1535) "does not use the phrase, either in the text or the chapter heading..., but he has it in 1 Chronicles 16:3 and Proverbs 15:7." Miles Smith used the same phrase in "The Translators to the Reader," the lengthy preface to the 1611 King James Bible, but by the seventeenth century the phrase had become very widespread indeed and had clearly achieved the status of a fixed phrase with allusive, quasi-proverbial, force.