[864] The origin at Sāvatthī (Sāvatthīnidānaṃ). Now at that time the group-of-six bhikkhus taught the Dhamma to a person in a vehicle. … "I will not teach the Dhamma to a person who is not sick who is in a vehicle"—thus the training is to be undertaken.
"Vehicle" (yāna) means: a palanquin (vayha), a chariot (ratha), a cart (sakaṭa), a carriage (sandamānikā), a sedan chair (sivikā), a litter (pāṭaṅkī).
The Dhamma should not be taught to a person who is not sick who is in a vehicle. Whatever bhikkhu, out of disrespect (anādariya), teaches the Dhamma to a person who is not sick who is in a vehicle, incurs an offense of wrong-doing (dukkaṭa).
There is no offense: if it is unintentional; if he is unmindful; if he does not know; if the person is sick; in emergencies; if he is insane; if he is the first offender (ādikammika).
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.