Thus I have heard: One time, the Buddha was staying at Anāthapiṇḍada’s Park in Jeta’s Grove of Śrāvastī.

It was then that the Bhagavān addressed the monks, “From the start, I do not see in this assembly a single thing that’s easily controlled and which brings a good result when its easily controlled. That thing is the heart.

“[Therefore,] monks, one should discern their heart and be well aware of its good roots. Thus, monks, you should train yourselves.”

When the monks heard what the Buddha taught, they rejoiced and approved.