Thus have I heard:
One time, the Budha was staying at Anaathapindidas Ashrama in Jetavana of Shraavastii.
At that time, Bhagavaan addressed the Bhikshus:
“In this assembly, I do not see a single dharma whereby, in the absence of sensual thought, sensual thought arises; and once arisen, it increases.
In the absence of angry thought, angry thought arises; and once arisen, it multiplies. In the absence of drowsy thought, drowsy thought arises; and once arisen, it grows.
In the absence of frivolous thought, frivolous thought arises; and once arisen, it expands. In the absence of doubtful thought, doubtful thought arises; and once arisen, it proliferates.
One should also contemplate the impure nature of foulness. If one entertains distracted thoughts, then in the absence of sensual thought, sensual thought arises; and once arisen, it increases.
Anger, drowsiness—where originally there was no doubt, doubt arises; and once arisen, it multiplies.
Therefore, O Bhikshus! Do not indulge in distracted thoughts; always remain focused. Thus, O Bhikshus! Should you train yourselves.”
When the bhikshus heard what the Budha said, they followed it with joy.