From:
Theravāda Vinaya Theravāda Collection on Monastic Law
Mahāvibhaṅga The Great Analysis
Sekhiyakaṇḍa The chapter on training
Kabaḷavagga The subchapter on mouthfuls
47. Hatthaniddhunakasikkhāpada 47. The training rule on shaking the hand
Tena samayena buddho bhagavā sāvatthiyaṁ viharati jetavane anāthapiṇḍikassa ārāme. At one time the Buddha was staying at Sāvatthī in the Jeta Grove, Anāthapiṇḍika’s Monastery.
Tena kho pana samayena chabbaggiyā bhikkhū hatthaniddhunakaṁ bhuñjanti …pe…. At that time the monks from the group of six ate shaking their hands. …
“Na hatthaniddhunakaṁ bhuñjissāmīti sikkhā karaṇīyā”ti. “‘I will not eat shaking my hand,’ this is how you should train.”
Na hatthaniddhunakaṁ bhuñjitabbaṁ. One should not eat shaking one’s hand.
Yo anādariyaṁ paṭicca hatthaniddhunakaṁ bhuñjati, āpatti dukkaṭassa. If a monk, out of disrespect, eats shaking his hand, he commits an offense of wrong conduct.
Anāpatti—There is no offense:
asañcicca, if it is unintentional;
assatiyā, if he is not mindful;
ajānantassa, if he does not know;
gilānassa, if he is sick;
kacavaraṁ chaḍḍento hatthaṁ niddhunāti, if he shakes the hand to discard trash;
āpadāsu, if there is an emergency;
ummattakassa, if he is insane;
ādikammikassāti. if he is the first offender.
Sattamasikkhāpadaṁ niṭṭhitaṁ. The seventh training rule is finished.