During the dispensation of Kassapa Buddha, Kondadhāna Thera was born as a tree spirit.
To test the friendship of two friendly monks he transformed himself into a beautiful woman and created suspicion between them. When one of the monks went into a grove to answer the call of nature, the woman accompanied him and came out together.
When the other monk saw this, he got angry and suspicious. So he left his friend because he judged him to be immoral.
When the Uposatha ceremony had to be performed, the friend refused to conduct it together with the alleged immoral monk.
Even when the accused monk protested his innocence, his friend did not believe him. He said that he saw the beautiful woman coming out of the grove with him.
Thereupon the tree spirit, seeing the seriousness of his misdeed, appeared before the two friends and explained his conduct.
The spirit’s aim was merely to test the strength of their friendship, but the effects were dire.
Disunity arose between the two friends and one accused the other of an offence of defeat.
When the tree spirit died he was reborn in hell and suffered for his evil kamma.
So to accuse a scrupulous monk as immoral, gives a result as bad as the five heinous crimes, the worst evils one can commit.
[The Buddha said: “Monks, these two individuals, if they do not correct themselves, will certainly suffer in hell as surely as one who carries a burden to his house, puts it down.
One who claims to be a monk, though he is not, and one who accuses an innocent monk of an offence of defeat.”
(Itivuttaka 48, Āpāyika Sutta).
Such a false accusation, being very serious, brings certain suffering in hell for the accuser, just as a burden carried on the head, will certainly be put down on reaching one’s house.
One who maintains a wrong view, and one who unjustly accuses an innocent monk of defeat will, after death, fall into hell. Unless the wrong view is renounced, a person will suffer in hell.
Likewise, if one does not ask for forgiveness from a monk one has unjustly accused of defeat, one will fall into hell.]
The tree spirit became a monk in the time of the Buddha, but due to his past misdeed, wherever he travelled, a woman always accompanied him.
Although he did not see this shadowing woman following after him, others saw her.
So people became suspicious, abusing him as immoral repeatedly.
He finally reached Arahantship, but the resultant bad kamma had to be paid off until he attained parinibbāna.
The key point to note is that the tree spirit had no intention to stigmatise or to attach fault. His aim was merely to test the bond of friendship. He had no anger against the monk.
Yet the results for his evil deed were serious, bringing evil results in his succeeding lives.
His evil deed in this case was that of presenting a scrupulous monk as immoral.
(Ref : A Manual of Dhamma. The Venerable Ledi Sayādaw.)