Ja 189 Sīhacammajātaka Fausböll, Five Jātakas, pp. 14 and 39; Rhys Davids, Buddhist Birth Stories, p. v. This is Aesop’s Ass in the Lion’s Skin.
The Story about the Lion’s Skin (2s)

In the present Kokālika wanted to be one of those who recited the scriptures, and was invited to do so, but when he appeared in front of the Saṅgha he could not remember one verse. The Buddha tells a story of a merchant who used to throw a lion-skin over his donkey before putting him out to graze. But when confronted by villagers he revealed his true nature by braying, and was beaten to death.

The Bodhisatta = the wise farmer (paṇḍitakassaka),
Kokālika = the jackal (sigāla),
Devadatta = the merchant (vāṇija).

Present Source: Ja 172 Daddara,
Quoted at: Ja 188 Sīhakoṭṭhuka, Ja 189 Sīhacamma.

Keywords: Imitation, Deceit, Animals.

“Nor lion, nor tiger I see.” [2.76] This story, like the last, was about Kokālika, told by the Teacher in Jetavana.

At this time we hear that there were a number of very learned monks in the district of Manosilā, who spoke out like young lions, loud enough to bring down the heavenly Ganges, while reciting passages of scripture before the Saṅgha. As they recited their texts, Kokālika (not knowing what an empty fool he showed himself) thought he would like to do the same. So he went about among the monks saying: “They don’t ask me to recite a piece of scripture. If they were to ask me, I would do it.” All the Saṅgha got to know of it and they thought they would try him. “Friend Kokālika,” they said, “give the Saṅgha a recital of some scriptures today.” To this he agreed, not knowing his folly; that day he would recite before the Saṅgha.

He first partook of gruel made to his liking, ate some food, and had some of his favourite soup. At sundown the gong sounded for sermon time; all the Saṅgha gathered together. The ‘yellow robe’ which he put on was blue as a bluebell; his outer robe was pure white. Thus clad, he entered the meeting, greeted the elders, stepped up to a Dhamma Seat under a grand jewelled pavilion, holding an elegantly carved fan, and sat down, ready to begin his recitation. But just at that moment beads of sweat began to start out all over him, and he felt ashamed. The first verse of the first verse he repeated; but what came next he could not think. So rising from the seat in confusion, he passed out through the meeting, and sought his own cell. Someone else, a real scholar, recited the scripture. After that all the monks knew how empty he was.

One day the monks fell a talking of it in the Dhamma Hall, “Friend, it was not easy to see formerly how empty Kokālika is; but now he has given tongue of his own accord, and shown it.” The Teacher entered, and asked what they were discussing together. They told him.

This time he wanted to intone. The Teacher on hearing of it told the following story.

In the past, when Brahmadatta was reigning in Benares, the Bodhisatta was born in a farmer’s family, and when he grew up he got a livelihood by tillage.

At the same time there was a merchant who used to go about hawking goods, which a donkey carried for him. Wherever he went, he used to take his bundle off the ass, and throw a lionskin over him, {2.110} and then turn him loose in the rice and barley fields. When the watchmen saw this creature, they imagined him to be a lion, and so did not come near him.

One day this hawker stopped at a certain village, and while he was getting his own breakfast cooked, he turned the ass loose in a barley field with the lionskin on. The watchmen thought it was a lion, and did not come near, but fled home and gave the alarm. All the villagers armed themselves, and hurried to the field, shouting and blowing on conchs and beating drums. The ass was frightened out of his wits, and gave a hee-haw! Then the Bodhisatta, seeing that it was a donkey, repeated the first verse:

1. “Nor lion nor tiger I see,
Not even a leopard is he:
But a donkey – the wretched old hack!
With a lion-skin over his back!”

As soon as the villagers learned that it was only an ass, they cudgelled him till they broke his bones, and then went off with the lion-skin. When the merchant appeared, and found that his ass had come to grief, he repeated the second verse:

2. “The donkey, if he had been wise,
Might long the green barley have eaten;
A lion-skin was his disguise:
But he gave a hee-haw, and got beaten!” [2.77]

As he was in the act of uttering these words, the ass expired. The merchant left him, and went his way.

After this discourse was ended, the Teacher identified the Jātaka, “At that time Kokālika was the ass, and the wise farmer was I myself.”