The Jataka, Volume I, tr. by Robert Chalmers, , at sacred-texts.com
"’Tis knowledge."--This story was told by the Master while at Jetavana about one who spoiled spirits.. Tradition says that Anātha-piṇḍika had a friend who kept a tavern. This friend got ready a supply of strong spirits which he sold for gold and for silver 1, and his tavern was crowded. He gave orders to his apprentice to sell for cash only, and went off himself to bathe. This apprentice, while serving out the grog to his customers, observed them sending out for salt and jagghery and eating it as a whet. Thought he to himself; "There can't be any salt in our liquor; I'll put some in." So he put a pound of salt in a bowl of grog, and served it out to the customers. And they no sooner took a mouthful, than they spat it out again, saying, "What have you been up to?" "I saw you sending for salt after drinking our liquor, so I mixed some salt in." "And that's how you've spoilt good liquor, you booby," cried the customers, and with abuse they got up one after another and flung out of the tavern. When the keeper of the tavern came home, and did not see  a single customer about, he asked where they had all got to. So the apprentice told him what had happened. Rating him for his folly, the man went off and told Anātha-piṇḍika. And the latter, thinking the story a good one to tell, repaired to Jetavana, where after due obeisance he told the Master all about it.
"This is not the first time, layman," said the Master, "that this apprentice has spoiled spirits. He did just the same once before." Then at Anātha-piṇḍika's request, he told this story of the past.
Once on a time when Brahmadatta was reigning in Benares, the Bodhisatta was the Treasurer of Benares, and had a tavern-keeper who lived under his protection. This man having got ready a supply of strong spirits, which he left his apprentice 2 to sell while he himself went off to bathe, during his absence his apprentice mixed salt with the liquor, and spoiled it just in the same way. When on his return the young man's guide and master 2 came to know what had been done, he told the story to the Treasurer. 'Truly,' said the latter, the ignorant and foolish, with every desire to do good, only succeed in doing harm.' And he recited this stanza:--
In these lines the Bodhisatta taught the truth.
Said the Master, "Layman, this same person spoiled spirits in the past as now." Then he shewed the connexion and identified the Birth by saying, "He who spoiled the spirits now was also the spoiler of the spirits in those bygone days, and I myself was then the Treasurer of Benares."
120:1 Apparently regarded as a 'Jewish' proceeding, as opposed to normal barter.
120:2 With a dry humour, the Pāli applies to the publican and his apprentice the terms normally applied to a religious teacher and his pupil.