Sahadhammamikavagga

Vinayapiṭaka · Parivāra · Vol. 8 · Section 368

[368] When bhikkhus have become quarrelsome, have become contentious, and have fallen into dispute, one who stands eavesdropping on them commits two offences (āpatti): he goes, thinking, "I shall listen" — an offence of wrong-doing (dukkaṭa); where he stands and hears — an offence requiring expiation (pācittiya).

English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.