Monks’ rules and their analysis
Monks’ Training (Sekhiya) 66
‘I will not teach dhamma to (someone) with a turban on his head (and) who is not ill,’ is a training to be observed.”
Turban on the head means: it is a turban when it does not let the ends of the hair be seen.
Dhamma should not be taught to (someone) with a turban on his head (and) who is not ill. Whoever out of disrespect teaches dhamma to (someone) with a turban on his head (and) who is not ill, 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 he shows the ends of the hair having caused them to be uncovered, if there are accidents, if he is mad, if he is the first wrong-doer.