Those who ‘observe’ the precepts loosely,
with some intention of possibly breaking them later
will find their misgivings correspondingly more difficult to repent.
Once when the Buddha Shakyamuni was in the world, there were two Bhikshus [monks] cultivating in the mountains. One day, one of the Bhikshus went down the mountain to get food and left the other one sleeping. In India at that time, the Bhikshus simply wore their sashes wrapped around them; they did not wear clothing underneath. This Bhikshu had shed his robe and was sleeping nude… At that time a woman happened to come along, and seeing the Bhikshu, she was aroused and took advantage of him. Just as she was running away from the scene, the other Bhikshu returned from town and saw her in flight. Upon investigation he found out that the woman had taken advantage of the sleeping Bhikshu, and he decided to pursue her, catch her, and take her before the Buddha in protest. He took out after her, and the woman became so reckless that she slipped off the road and tumbled down the mountain to her death.
So one Bhikshu had violated the precept against sexual activity and the other had broken the precept against killing. Although the [second] Bhikshu hadn’t actually pushed her down the mountain, she wouldn’t have fallen if he hadn’t been pursuing her. ‘What a mess.’ concluded the two Bhikshus. Messy as it was, they had to go before the Buddha and describe their offenses. The Buddha referred them to the Venerable Upali. But when Venerable Upali heard the details, his verdict was that, indeed, one had violated the precept against sexual activity and the other against killing, offenses which cannot be absolved. ‘You’re both going to have to endure the hells in the future,’ he concluded. Hearing this, the two monks wept, and they went about everywhere trying to find someone who could help them.
Eventually, they found the Great Upasaka Vimalakirti, who asked why they were crying. When they had related their tale, he pronounced his judgment that they had not violated the precepts. ‘If you can be repentant,’ he said, ‘then I can certify that you didn’t break the precepts.’ ‘How can that be?’ they asked. ‘The nature of offenses is basically empty,’ replied the Upasaka. ‘You did not violate the precepts intentionally, and so it doesn’t count. It is an exception.’ Hearing this explanation by the Great Teacher Vimalakirti, the two Bhikshus were enlightened on the spot and were certified as attaining the fruition… So there are many exceptions within the prohibitive precepts. But if people always look to the exceptions, they will simply not hold the precepts. They will beg the question. So the Buddha did not speak much about this aspect.” [Master Hui Seng]
Thus Have I Heard: Buddhist Parables & Stories