Bhagavad Gita Verse 14, Chapter 17

devadvijagurupraajnyapoojanam shauchamaarjavam |
brahmacharyamahimsaa cha shaareeram tapa uchyate || 14 ||
 
Worship of the deities, the twice born, teachers and the learned, purity, straightforwardness, chastity and non violence, these are called penance of the body.
 
deva : deities
dvija : twice born
guru : teacher
praajnya : learned
poojanam : worship
shaucham : purity
aarjavam : straightforwardness
brahmacharyam : chastity
ahimsaa : non violence
cha : and
shaareeram : of the body
tapaha : penance
uchyate : called
 
So far, Shri Krishna described the three types of food and worship so that we can use them to analyze the texture of our faith. He now begins the topic of tapas, which means penance or austerity. Through tapas we ensure that the energy that we derive from consuming food can be conserved and channeled into our actions. This tapas or penance is also of three types, saattvic, raajasic and taamasic. But penance itself needs to be broken down into its three main components first. Here, we examine the first component which is bodily or physical penance, shaaririka tapas.
 
Penance of the body begins with bowing down to, respecting, and serving our deities, our elders and our teachers. Deities also means the gods representing elemental forces such as Varun, lord of the seas. This means that we should worship and take care of all the natural resource this world has to offer. Offering service to something greater than us also has the effect of checking our aham, our ego, our illusory notion of who we are. It increases our humility and decreases our individuality.
 
Shaucham refers to purity of our body and our surroundings. If we keep our room unclean or cluttered, it is an indication that our mind is also unclean, or is cluttered with useless thoughts. Aarjavam or straightforwardness refers to our posture. We will not be able to meditate unless we are able to maintain an erect posture. This straightforwardness of the body is also a pointer to making our thinking straightforward, without any trace of deceit. Brahmacharyam refers to stopping our checking the excessive straying of our sense organs into their respective objects, like watching too much TV or consuming a lot of rich food. Ahimsa or non violence prevents us from harming anyone or anything using our body.