The Jataka, Volume I, tr. by Robert Chalmers, , at sacred-texts.com
"Trust not the trusted." This story was told by the Master while at Jetavana, about taking things on trust.
Tradition tells us that in those days the Brethren, for the most part, used to rest content if anything was given them by their mothers or fathers, brothers or sisters, or uncles or aunts, or other kinsfolk. Arguing that in their lay state they had as a matter of course received things from the same hands, they, as Brethren,
likewise shewed no circumspection or caution before using food, clothing and other requisites which their relations gave them. Observing this the Master felt that he must read the Brethren a lesson. So he called them together, and said, "Brethren, no matter whether  the giver be a relation or not, let circumspection accompany use. The Brother who without circumspection uses the requisites which are given to him, may entail on himself a subsequent existence as an ogre or as a ghost. Use without circumspection is like unto taking poison; and poison kills just the same, whether it be given by a relative or by a stranger. There were those who in bygone days actually did take poison because it was offered by those near and dear to them, and thereby they met their end." So saying, he told the following story of the past.
Once upon a time when Brahmadatta was reigning in Benares, the Bodhisatta was a very wealthy merchant. He had a herdsman who, when the corn was growing thick, drove his cows to the forest and kept them there at a shieling, bringing the produce from time to time to the merchant. Now hard by the shieling in the forest there dwelt a lion; and so afraid of the lion were the cows that they gave but little milk. So when the herdsman brought in his ghee one day, the merchant asked why there was so little of it. Then the herdsman told him the reason. "Well, has the lion formed an attachment to anything?" "Yes, master; he's fond of a doe." "Could you catch that doe?" "Yes, master." "Well, catch her, and rub her all over with poison and sugar, and let her dry. Keep her a day or two, and then turn her loose. Because of his affection for her, the lion will lick her all over with his tongue, and die. Take his hide with the claws and teeth and fat, and bring them back to me." So saying, he gave deadly poison to the herdsman and sent him off. With the aid of a net which he made, the herdsman caught the doe and carried out the Bodhisatta's orders.
As soon as he saw the doe again, the lion, in his great love for her, licked her with his tongue so that he died. And the herdsman took the lion's hide and the rest, and brought them to the Bodhisatta, who said, "Affection for others should be eschewed. Mark how, for all his strength, the king of beasts, the lion, was led by his sinful love for a doe to poison himself by licking her and so to die." So saying, he uttered this stanza for the instruction of those gathered around:--
Such was the lesson which the Bodhisatta taught to those around him. After a life spent in charity and other good works, he passed away to fare according to his deserts.
His lesson ended, the Master identified the Birth by saying, "I was the merchant of those days."
[Note. Cf. Böhtlingk's "Indische Sprüche," (1st ed.) Nos. 1465-7 and 4346.]