Thus have I heard:
One time, the Budha was staying at Anaathapindidas Ashrama in Jetavana of Shraavastii.
The Bhagavaan addressed the Bhikshus: “I have not seen anything that changes as swiftly as the mind – so fast it defies comparison. Like a monkey leaping from branch to branch, the mind jumps from thought to thought without stability. One moment it thinks this, the next moment that, so quickly that it cannot be grasped by ordinary means.
Therefore, O Bhikshus! Ordinary people cannot truly observe the workings of their own minds. Thus, O Bhikshus! You should constantly discipline your minds and direct them toward the wholesome path. This is how you should train yourselves.”
When the bhikshus heard what the Budha said, they followed it with joy.