The Jataka, Vol. II, tr. by W.H.D. Rouse, , at sacred-texts.com
"The wicked kills," etc.--This is a story which the Master told while staying in his gabled chamber near Vesāli, about Sīhasenāpati.
It is said that this man, after he had fled to the Refuge, offered hospitality and then gave food with meat in it. The naked ascetics on hearing this were angry and displeased; they wanted to do the Buddha a mischief; "The priest Gotama," sneered they, "with his eyes open, eats meat prepared on purpose for him."
The Brethren discussed this matter in their Hall of Truth: "Friend, Nāthaputta the Ascetic 1 goes about sneering, because, he says, 'Priest Gotama eats meat prepared on purpose for him, with his eyes open'." Hearing this, the Master rejoined:--"This is not the first time, Brethren, that Nāthaputta has been sneering at me for eating meat which was got ready for me on purpose; he did just so in former times. And he told them an old-world tale.
Once on a time, when Brahmadatta was king of Benares, the Bodhisatta was born a brahmin. When he came of age he embraced the religious life.
He came down from Himalaya to get salt and seasoning, and next day walked the city, begging alms. A certain wealthy man designed to annoy the ascetic. So he brought him to his dwelling, and pointed out a seat, and then served him with fish. After the meal, the man sat on one side, and said,
"This food was prepared on purpose for you, by killing living creatures. Not upon my head is this wrong, but upon yours!" And he repeated the first stanza:--
 On hearing this, the Bodhisatta recited the second stanza:--
And the Bodhisatta with these words of instruction rose from his seat and departed.
This discourse ended, the Master identified the Birth: "Nāthaputta, the Naked Ascetic was this wealthy man, and I was the ascetic."
182:1 He is one of the six titthiyas (Heretics), and generally called Nātaputta (which is probably the right spelling here). The 'naked ascetics' were probably the Jains.
182:2 "..Ṭhose who take life are in fault, but not the persons who eat the flesh; my priests have permission to eat whatever food it is customary to eat in any place or country, so that it be done without the indulgence of the appetite, or evil desire." Hardy, Manual, p. 327.