DO NO EVIL AGAIN AND AGAIN
Papan ce puriso kayira na tam kayira punappunam
Na tamhi chandam kayiratha dukkho papassa uccayo.
Should a person commit evil, he should not do it again and again; he should not find pleasure therein; painful is the accumulation of evil. 
Once there was a monk by the name of Seyyasaka, who was not happy with the religious life and was in the habit of stimulating himself sexually. When the Buddha heard about this, he admonished the monk to refrain from acts that would lead him farther away from the gaining of purity. At the same time, the Buddha introduced the disciplinary rule for bhikkhus to abstain from such indulgence in sensual pleasure. He called them offences which require censure. Then, the Buddha added, 'This kind of act can lead to suffering.'