[67] Now at that time a certain bhikkhu, having gone for the day's abiding in the Jātiyā Grove at Bhaddiya, was lying down. His limbs were stiff with wind. A certain woman, seeing him, sat down upon his male organ (aṅgajāta), took as much as she wished, and departed. The bhikkhu, seeing the wetness, reported this matter to the Blessed One.
"Bhikkhus, in five ways the male organ becomes erectile (kammaniya): through lust, through feces, through urine, through wind, and through being bitten by caterpillar insects (uccāliṅgapāṇaka). In these five ways, bhikkhus, the male organ becomes erectile. It is impossible, bhikkhus, there is no chance, that that bhikkhu's male organ could have become erectile through lust. That bhikkhu, bhikkhus, is an arahant (arahaṃ). There is no offence (anāpatti), bhikkhus, for that bhikkhu."
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.