In the fourteenth section of the Ten Procedures to Be Recited it says:
When Rahula, the Buddha’s son, was a novice, he took to
spending his nights in the Buddha’s lavatory. The Buddha, fully aware
of what His son was doing, patted Rahula on the head with His right
hand and recited this verse:
My son, it was not to be poor or in want,
Nor to rid yourself of fortune or position,
But simply to seek the Way that you left home,
Which will surely bring hardships enough to bear.
So, you see, the Buddha’s temple had its lavatory too. The form for dignified
behavior in the Buddha’s lavatory was to wash oneself clean, and the Ancestors, in
turn, passed this on to us. The conduct of the Buddhas has still been preserved: to
follow the ancient ways is a great joy and something indeed hard to come by.
Further, thankfully, the Tathagata gave voice to the Dharma for Rahula whilst in
the lavatory. The lavatory was a place fit for the Buddha to turn the Wheel of the
Dharma. How to conduct oneself in that training place of the Way is what the
Buddhas and Ancestors truly Transmitted.