Monks’ rules and their analysis
Monks’ Training (Sekhiya) 64
‘I will not teach dhamma to (someone) on a bed and who is not ill,’ is a training to be observed.”
Dhamma should not be taught to (someone) on a bed (and) who is not ill. Whoever out of disrespect teaches dhamma to (someone) on a bed and even lying on the ground (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.