Quatrain 29

Waste not your Hour, nor in the vain pursuit
Of This and That endeavour and dispute;
Better be jocund with the fruitful Grape
Than sadden after none, or bitter, Fruit.

FitzGerald, Stanza LIV, 4th ed.

According to both Heron-Allen (p. 85) and Arberry (Romance ... 216), the source-quatrain is thought to come from the Bodleian-Ouseley MS 50.  For the Ouseley as below and stabs at renditions select this link to omariana.nl

آنان که اسیر عقل و تمییز شدند
در حسرت هست و نیست ناچیز شدند
 رو بی‌خبری و آب انگور گزین
کان بی‌خبران بغوره میویز شدند


aanaan ke asir-e aql o tamyiz shodand
dar hasrat-e hast o nist naachiz shodand
row bikhabari o aab-e angur gozin
kaan bikhabaraan beghure miviz shodand

Those who are the slaves of intellect and hair-splitting,
Have perished in bickerings about existence and non-existence;
Go, thou dunce! and choose (rather) grape juice,
For the ignorant from (eating) dry raisins,
have become (like) unripe grapes (themselves).


Heron-Allen adds two footnotes: the first on hair-splitting, he notes "literally, 'discernment'"; and in the second, he speaks of the odd and inaccurate translation of the final line: "The obscurity of the meaning here baffles satisfactory translation.  Prof. Cowell says: 'I would take it as a sarcasm.  "Those fools with their unripe grapes become (in their own eyes) pure wine" (می ویز).
mey-e viz or preferably mey-e vizh, (Steingass, where only vesh occurs with the meaning of pure or unadulterated) cannot stand metrically. 

Arberry is right to object to both Heron-Allen and Cowell on this line. He feels that FitzGerald was also misled (I summarize Arberry here; viewers will find his arguments on page 216 of Romance ...) But as we shall see Arberry is wide of the mark himself: "His [Heron-Allen's] troubles began when he incorrectly surmised that ghura meant 'dry raisins'; in fact it means 'unripe grapes'.  By looking into the dictionary he could have avoided this error, and also found that miviza explained as 'convolvulus' ... From this he should have proceeded to understand Omar's meaning; the 'ignorant' philosophers attach themselves like bindweed (and after their death actually become bindweed) about the unripe grapes of reason, instead of enjoying, like himself, the sweet wine of unreason." And Arberry translates:

Those who became the prisoners of reason and discrimination
became nothing in sighing over Being and Not-being:
go, ignorant one, and choose the juice of the grape,
for those ignorant ones became convolvulus
about the unripe grape.

Arberry has a nice argument, but this is not convolvulus/bindweed.  The word is miviz not miviza/miwiza.  It means currants or raisins and miviz is apparently an alternate and earlier from of maviz , کشمش درشت و سیاه"plump black raisins/currants", Anvari, bozorg-e sokhan, 7. 7508. Whinfield, quatrain 216, catches the meaning: "gets shriveled up like old dried grapes" and Saidi, quatrain 60, captures the intent in his note, p. 246: "The purport of the ruba'i is that those wizards (fools) who were ghoorah, namely, unripe (used metaphorically to mean "ignorant") when starting, spent a lifetime studying and inquiring into the nature of "Being" and "not-being" and, at the end, without reaching the sweet stage of ripeness (i.e., the state of perception) shriveled into raisins."

As Aminrazavi tells us, the sort of vain philosophical argument, the subject of the first two lines of the quatrain, detracts from and obfuscates as Khayyaam sees it, the present, the here and now, and what matters (Wine of Wisdom, chapter 3, passim). Also it is possible that Khayyaam had in mind the rigid authorities of his day, those who espoused faith and rejected open-minded inquiry.
In this chapter, Aminrazavi contends that many of these khayyaamic quatrains were "a reaction against the rise of dogmatism." The quatrain likely carries both interpretations and serves the purpose of protest poetry through disguise and ambiguity. 

Those who live and select
by pride, by intellect,
who vie and sigh
for what is and is not,
captives they become
and nothing at all.
In your ignorance you'll make
a wise choice by the grape;
our pedants never ripen--
they shrinkle into raisins.