Ovādavagga

Vinayapiṭaka · Parivāra · Vol. 8 · Section 318

[318] A bhikkhu who, having made an arrangement with a bhikkhunī, boards the same boat commits two offenses (āpatti): while he is boarding, there is an offense of wrong-doing (dukkaṭa) for the act; when he has boarded, there is an offense entailing expiation (pācittiya).

English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.

This passage also appears in 1 other place

Vol. 8 · Section 332 — Acelakavagga