戒（siila）或戒行（siilana）為善良的利己又利他的品行，重視有善良 的動機以及美好的成果。持善戒、持不善戒，犯戒、破戒，戒之雜染、戒之淨化， 皆須「思（cetana）」心所法之審慮、決定，在意識清醒下所為。論藏提出「云何 是戒？」《無礙解道》的答案是︰「思（cetanaa）是戒也，心所（cetasika）是戒 也，律儀（sa^mvara防護）是戒也，不犯（aviitikkama）是戒也。」《中阿含 五 支物主經》釋尊開示︰「此善戒從何而生？我說彼所從生，當知從心生。」 《四部阿含》說明有種種心態 生起持善戒︰1.從怖苦心持善戒。2.從畏罪心 持善戒。3.從求福心持善戒。4.從兩利心持善戒。5.從慚愧心持善戒。6.從慈悲心 持善戒。7.從自通（attuupanaaika）心持善戒。8.從菩提心持善戒。《阿含》所要 求的四種戒，是以正念正知 調伏身心，使心性之各部分──知、情、意得以調 理，平等地改善人格，具足戒清淨，成就戒法身。

　　　　　Sila or silana is moral discipline, which is conducive to both the well-being of oneself and others. Most importantly, it is the root of good intentions, which in turn produces an excellent result. Whether possesses good or evil sila, transgresses or breaks sila, or defiles or purifies sila follows investigation and is determined by volition in the belongings of mind, which is done with clear consciousness. A collection of commentaries mentions "What is sila"? The Patisambhida provides the answer: "Volition is sila. Consciousness-concomitant is sila. Restrain is sila. Nontransgression is sila". In the Pabcakavga thapati sutra of the Madhyama Agama, Lord Wakya taught "What is the source of the excellent sila? I will explain their origin. They should be known that the origin is in the mind." Four collections of Agama explain that there are many states of mind, which produce and maintain sila. These states arise from: Fear of suffering. Fear of the consequences of transgression. Wishing for a state of well-being. Wishing to benefit oneself and others.Feeling of shame.A compassionate mind.A self-reflection mind. An enlightened mind. The Agama requires four kinds of sila: to transform body and mind through correct mindfulness and correct awareness, to make each aspect of the mind──intellect, emotion, and will──flexible so that one's personality can improve, to be endowed with the purity of sila, and to realize the dhammakaya of sila.