We read in the 'Discourse on an exhortation to Rāhula at Ambalatthikā’ (Middle Length Sayings II, no. 61, Bhikkhu-vagga) that the Buddha spoke to his son Rāhula about lying. The Buddha said:
Even so, Rāhula, of anyone for whom
there is no shame at intentional lying,
of him I say that there is no evil he cannot do.
Wherefore, for you, Rāhula,
'I will not speak a lie, even for fun' - -
this is how you must train yourself, Rāhula.
Lying can also be done with dosa-mūla-citta and this is the case when one
wants to harm someone else.
As regards slandering, we all are inclined to talk about other. When there is
no intention to harm the reputation of others, there is no akusala kamma-
patha. However, when talking about others becomes a habit, there can easily
be an occasion for akusala kamma-patha. This kind of akusala kamma-patha
is performed with lobha-mūla-citta if one slanders in order to obtain
something for oneself or to please others. It is performed with dosa-mūla-
citta if one wants to harm someone else. We will be less inclined to talk about
others or to judge them when we see ourselves and others as phenomena
which arise because of conditions and which do not stay. At the moment we
talk about other people's actions, these phenomena have fallen away already;
What they said or did exists no more.
Rude speech is performed with dosa-mūla-citta.
Frivolous talk is talk about idle, senseless things. This kind of talk can be
performed with lobha-mūla-citta or by dosa-mūla-citta. Frivolous talk is not
always akusala kamma patha. It can be done with by akusala citta which does
not have the intensity of akusala kamma-patha.