The Jataka, Vol. III, tr. by H.T. Francis and R.A. Neil, , at sacred-texts.com
"Long I held," etc.—This story was told by the Master at Jetavana, concerning a heron that lived in the house of the king of Kosala. She carried messages, they say, for the king, and had two young ones. The king sent this bird with a letter to some other king. When she was gone away, the boys in the royal family squeezed the young birds to death in their hands. The mother bird came back and missing her young ones, asked who had killed her offspring. They said, "So and So." And at this time there was a fierce and savage tiger kept in the palace, fastened by a strong chain. Now these boys came to see the tiger and the heron went with them, thinking, "Even as my young ones were killed by them, just so will I deal with these boys," and she took hold of them and threw them down at the foot of the tiger. The tiger with a growl crunched them up. The bird said, "Now is the wish of my heart fulfilled," and flying up into the air made straight for the Himālayas. On hearing what had happened they started a discussion in the Hall of Truth, saying,  "Sirs, a heron, it is said, in the king's palace threw down before a tiger the boys who killed her young ones, and when she had thus brought about their death, she made off." The Master came and inquired what it was the Brethren were discussing and said, "Not now only, Brethren, but formerly also did she bring about the death of those who killed her young ones." And herewith he related a legend of the past.
Once upon a time the Bodhisatta at Benares ruled his kingdom with justice and equity. A certain heron in his house carried messages for him. And so on just as before. But the special point here is that in this case the bird, having let the tiger kill the boys, thought, "I can no longer remain here. I will take my departure, but though I am going away I will not leave without telling the king, but as soon as I have told him I will be off." And so she drew nigh and saluted the king, and standing a little way off said, "My lord, it was through your carelessness that the boys killed my young ones, and under the influence of passion I in revenge caused their death. Now I can no longer live here." And uttering the first stanza she said:
Honour great I did receive,
It is due to act of thine
I am now compelled to leave.
The king on hearing this repeated the second stanza:
Wrong with equal wrong repay,
Then his anger should abate;
So, good heron, prithee stay.
 Hearing this the bird spoke the third stanza:
As of old be made at one:
Nought, O king, can keep me here,
Lo! from henceforth I am gone.
The king, on hearing this, spoke the fourth stanza:
With the wronged wrong-doer may
Live in peace and harmony:
So, good heron, prithee, stay.
The bird said, "As things are, I cannot stay, my lord," and saluting the king she flew up into the air and made straight for the Himālayas.
The Master, his lesson ended, thus identified the Birth: "The heron in the former tale was the heron in this, but the king of Benares was myself."