Yama– the Yoga Upanishads Explains

Yama – Non-violence, truth, abstinence from stealing, celibacy, compassion, rectitude, forbearance, fortitude, temperance in food, and cleanliness are the ten Yamas.

1. Non-violence (Ahimsa) – Abstinence from causing pain always, in all beings, by thought, word of mouth and deed, is termed as non-violence.

1. Truthfulness (Satya) – Firmly believe that all that exists is the supreme Brahman and not anything else. The uttering of what is truth, conducive to the welfare of beings, by thought, word and deed, is termed as truthfulness.
2. Abstinence from stealing (Asteya) – the total abstinence of the mind equally from straw, gem, gold even the pearl belonging to others to be abstinence from stealth. The absence of covetousness towards others’ wealth, by thought, word of mouth and deed is non-stealth.
3. Celibacy (Brahamcharya) – the complete abstinence from the contact with women by means of the body, word of mouth and the mind.
4. Compassion (Daya) – That behaviour towards all beings, as towards one’s self, by body, mind and word of mouth is known as compassion.
5. Rectitude (Arjava, righteousness) – Uniformity in behaviour towards one’s sone, friend, wife, enemy as well as one’s own self, under all circumstances. Abhorrence of things prohibited, in thought, word and deed, is termed as rectitude.
6. Forbearance (Ksama) – Abstinence from losing temper, when provoked by enemies, by body, mind and speech is forbearance.
7. Firmness (Dhrti) – Firmness is the unswerving belief to the effect – “I am the Atman and am nothing else.” Steadiness of mind, under all circumstances, whether at the loss of wealth and the bereavement of one’s relations and friends or at their acquisition afresh, is termed as fortitude.
8. Temperance in Food (Mitahara) – Leaving off a fourth from the food served, which is moderate and pure, eating, so as to conduce to the attainment of Yoga, is Temprance in food.
9. Cleanliness (Sauchas) – Cleanliness of the exterior; while contemplation on the Supreme Being is mental Cleanliness.  Cleanliness with the aid of earth and water is external. Purity of mind is internal. That should be attained through study of wisdom pertaining to the Atman.

Four-fold Yamas -
The four-fold Yamas are as follows –

1. The conquest of cold and heat, as well as the craving for food and sleep resulting from the giving up of the misconception, that what relates to the body relates to the Atman;
2. Tranquillity, under all circumstances, with the dawning of the knowledge, that there is nothing unattainable by the Atman;
3. Non-swaying of the mind, from the high ideal set before it;
4. Control of the senses and their functioning on the objects of desire.