One does not need be a philosopher to have a working theory of morality. Nor need one be an economist to have a working theory of value. One can find implicit theories in the writings of any thoughtful person; and the ancient Greek poet Hesiod was a very thoughtful man.
Conversely, one can be a philosopher or an economist and still have their prejudices corrupt their lofty theories One can find such prejudices in the writings of any biased person; and Adam Smith was a very biased man.
Or at least it can be argued he was. Murray N. Rothbard, to my mind, has convincingly made the case1 that Adam Smith's labor theory of value was largely based on a Calvinist bias for work (for its own sake) and against consumption (except as a requirement to sustain work).
At first glance, one might see a similar ethic in Hesiod's Works and Days: particularly in the admonishments he gives his brother Perses to work. This would be a poor and shallow understanding of Hesiod's credo. Hesiod does not make a fetish of labor: far from it. In fact, he longs for the Age of Gold in which, as he believes, men were, "entirely free from toil."2
They had all good things: the grain-giving field bore crops of its own accord, much and unstinting3
And Hesiod sorrowfully regrets being born in the Age of Iron in which man must toil miserably all day stooped over the ground. For Hesiod, work is valued only by virtue of its role in satisfying needs: satiating hunger, keeping out the cold, and even enjoying a drink now and then.
It might seem strange to find religion in the Wealth of Nations and a subjective utility theory of value in a 2,700 year old poem which also discusses Zeus and Hephaestus; but it should not. Much folly can be found in the twisted sophistries of intellectuals, and much wisdom can be found in the simple beliefs of honest men.
1Murray N. Rothbard, An Austrian Perspective on the History of Economic Thought, Volume 1: Economic Thought Before Adam Smith, p. 457
2Hesiod, Works and Days, verse 109-126