Monks’ rules and their analysis
Monks’ Training (Sekhiya) 58
‘I will not teach dhamma to (someone) who is not ill (and) who has a staff in his hand,’ is a training to be observed.”
Staff means: (the size of) four hands of a man of average height. Bigger than that it is not a staff, smaller it is not a staff.
Dhamma should not be taught to (someone) who has a staff in his hand (and) who is not ill. Whoever out of disrespect teaches dhamma to (someone) who has a staff in his hand (and) who is not ill, there is an offence of wrong-doing.
There is no offence if it is unintentional … if he is the first wrong-doer.