Monks’ rules and their analysis
Monks’ Training (Sekhiya) 65
‘I will not teach dhamma to (someone) who is sitting down, lolling (and) who is not ill,’ is a training to be observed.”
Dhamma should not be taught to (someone) sitting down, lolling, (and) who is not ill. Whoever out of disrespect teaches dhamma to (someone) who is sitting down, lolling on his hands or lolling on his robes (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.