Thus have I heard:
One time, the Budha was staying at Anaathapindidas Ashrama in Jetavana of Shraavastii.
Then the Bhagavaan addressed the Bhikshus: “Within this Dharma, I find no method more effective than this:
that can prevent unarisen sensual thoughts from arising and can abandon arisen sensual thoughts;
that can prevent unarisen thoughts of hatred from arising and can abandon arisen thoughts of hatred;
that can prevent unarisen thoughts of sloth from arising and can abandon arisen thoughts of sloth;
that can prevent unarisen frivolous thoughts from arising and can abandon arisen frivolous thoughts;
that can prevent unarisen doubtful thoughts from arising and can abandon arisen doubtful thoughts.
You should also contemplate the impurity of body – foulness.
Having contemplated the impurity of body – foulness, unarisen sensual thoughts do not arise and arisen ones are abandoned; unarisen hatred does not arise and arisen hatred is abandoned; up to and including doubt, unarisen doubtful thoughts do not arise and arisen doubtful thoughts are abandoned.
Therefore, Bhikshus, you should always be mindful to contemplate the perception of impurity. Thus, Bhikshus, should you train yourselves.”
When the bhikshus heard what the Budha said, they followed it with joy.