Theravāda Vinayapiṭaka
Monks’ rules and their analysis
Monks’ Training (Sekhiya) 74
… in Anāthapiṇḍika’s monastery. Now at that time the group of six monks eased themselves and spat on green corn … “…
‘I will not ease myself or spit, if not ill, on green corn,’ is a training to be observed.”
One should not ease oneself or spit, if not ill, on green corn. Whoever out of disrespect eases himself or spits, if not ill, on green corn, there is an offence of wrong-doing.
There is no offence if it is unintentional, if he is not thinking, if he does not know, if he is ill, if done where there is no green corn he spreads green corn over it, if there are accidents, if he is mad, if he is the first wrongdoer.