The Jataka, Volume I, tr. by Robert Chalmers, , at sacred-texts.com
"For universal application."--This story was told by the Master while at Jetavana, about the Elder Lāḷudāyi who is said to have had a knack of always saying the wrong thing. He never knew the proper occasion for the several teachings. For instance, if it was a festival, he would croak out the gloomy text 1, "Without the walls they lurk, and where four cross-roads meet." If it was a funeral, he would burst out with "Joy filled the hearts of gods and men," or with "Oh may you see  a hundred, nay a thousand such glad days!"
Now one day the Brethren in the Hall of Truth commented on his singular infelicity of subject and his knack of always saying the wrong thing. As they sat talking, the Master entered, and, in answer to his question, was told the subject of their talk. "Brethren," said he, "this is not the first time that Lāḷudāyi's folly has made him say the wrong thing. He has always been as inept as now." So saying he told this story of the past.
Once on a time when Brahmadatta was reigning in Benares, the Bodhisatta was born into a rich brahmin's family, and when he grew up, was versed in all knowledge and was a world-renowned professor with five hundred young brahmins to instruct.
At the time of our story there was among the young brahmins one who always had foolish notions in his head and always said the wrong thing; he was engaged with the rest in learning the scriptures as a pupil, but because of his folly could not master them. He was the devoted attendant of the Bodhisatta and ministered to him like a slave.
Now one day after supper the Bodhisatta laid himself on his bed and there was washed and perfumed by the young brahmin on hands, feet and back. And as the youth turned to go away, the Bodhisatta said to him, "Prop up the feet of my bed before you go." And the young brahmin propped up the feet of the bed on one side all right, but could not find anything to prop it up with on the other side. Accordingly he used his leg as a prop and passed the night so. When the Bodhisatta got up in the morning and saw the young brahmin, he asked why he was sitting there. "Master," said the young man, "I could not find one of the bed supports; so I've got my leg under to prop it up instead."
Moved at these words, the Bodhisatta thought, "What devotion! And to think it should come from the veriest dullard of all my pupils. Yet how can I impart learning to him?" And the thought came to him that the best way was to question the young brahmin on his return from gathering firewood and leaves, as to something he had seen or done that day; and then to ask what it was like.  "For," thought the master, "this will lead him on to making comparisons and giving reasons, and the continuous practice of comparing and reasoning on his part will enable me to impart learning to him."
Accordingly he sent for the young man and told him always on his return from picking up firewood and leaves to say what he had seen or eaten or drunk. And the young man promised he would. So one day having seen a snake when out with the other pupils picking up wood in the forest, he said, "Master, I saw a snake." "What did it look like?" "Oh, like the shaft of a plough." "That is a very good comparison. Snakes are like the shafts of ploughs," said the Bodhisatta, who began to have hopes that he might at last succeed with his pupil.
Another day the young brahmin saw an elephant in the forest and told his master. "And what is an elephant like?" "Oh, like the shaft of a plough." His master said nothing, for he thought that, as the elephant's trunk and tusks bore a certain resemblance to the shaft of a plough, perhaps his pupil's stupidity made him speak thus generally (though he was thinking of the trunk in particular), because of his inability to go into accurate detail,
A third day he was invited to eat sugar-cane, and duly told his master. "And what is a sugar-cane like?" "Oh, like the shaft of a plough." .,That is scarcely a good comparison," thought his master, but said nothing. Another day, again, the pupils were invited to eat molasses with curds and milk, and this too was duly reported. "And what are curds and milk like?" "Oh, like the shaft of a plough." Then the master thought to himself, "This young man was perfectly right in saying a snake was like the shaft of a plough, and was more or less right, though not accurate, in saying an elephant and a sugar-cane had the same similitude. But milk and curds (which are always white in colour) take the shape of whatever vessel they are placed in;  and here he missed the comparison entirely. This dullard will never learn." So saying he uttered this stanza:--
His lesson ended, the Master identified the Birth by saying, "Lāḷudāyi was the dullard of those days, and I the professor of world-wide renown."
271:1 For this quotation see the Khuddaka Pātha edited by Childers (J. R. A. S. 1870, p. 319).