dravyayajnaas tapoyajnaa yogayajnaastathaa'pare
    swaadhyaaya jnaanayajnaashcha yatayah samshitavrataah  // 4.28 //

Others again offer wealth,  austerity and Yoga as sacrifice, while the ascetics of self-restraint and rigid  vows offer study of scriptures and knowledge as sacrifice.

Dravya Yagna: Charity and distribution of honestly acquired wealth  in a spirit of devotion in the service of the community is called Dravya yagna.  Wealth includes love, kindness, sympathy and affection also.

Tapo Yagna: Offering of a life of austerity to The Lord in a spirit  of dedication so that the seeker may attain a little self-control.

Yoga Yagna: Yoga is an attempt to grow from the lower in us to the  higher standard of divine living; it comprises such practices as breath-control  and the withdrawal of the mind from the objects of the world.

Swadhyaya Yagna: This means study and understanding of the  scriptures without which no progress in spiritual practices is possible. It  also implies introspection.

Jnana Yagna: It is that activity in man by which he renounces all  his ignorance into the fire of knowledge kindled by him in him. This has two  aspects - negation of the false and assertion of the real nature of the Self. These  two activities are undertaken during the seeker's meditation.

All these five methods of  self-development can be practiced only by him who is sincere and consistent in  his practices.

apaane juhwati praanam praane'paanam tathaa'pare
    praanaapaana gatee ruddhwaa praanaayaamaparaayanaah  // 4.29 //

Others offer as sacrifice the  out-going breath in the in-coming and the in-coming in the out-going,  restraining the courses of the out-going and in-coming breaths, solely absorbed  in the restraint of breath.

Sri Krishna explains here  Pranayama as another technique for self-control. Pranayama consists of three  processes viz.
• Puraka        :   process of filling in the breath
• Rechaka     :   process of blowing out the  breath 
• Kumbhaka:    process of holding the breath for some time.

Puraka and Rechaka are alternated  by an interval of Kumbhaka. This process of  Puraka-Kumbhaka-Rechaka-Kumbhaka-Puraka when practiced in the prescribed manner  becomes the method of Pranayama.   Pranayama is referred to here as a Yagna where the practitioner offers  all the five subsidiary Pranas into the main Prana. Prana does not merely mean  breath. It indicates the various manifested activities of life in a living  body.

Generally five different Pranas  are enumerated corresponding to different functions in every living body viz. 
• function of perception - prana 
• function of excretion - apana 
• function of digestion and assimilation - samana 
• circulatory system which distributes food to all  parts of the body  - vyana and 
• capacity of a living creature to improve himself  in his mental outlook and intellectual life - udana.

These activities of life are  brought under the perfect control of the individual through the process of  Pranayama so that a seeker can gain capacity to withdraw completely all his  perceptions of the outer world for gaining the knowledge of the Self.

apare niyataahaaraah praanaan praaneshu juhwati
    sarve'pyete yajnavido yajnakshapita kalmashaah  // 4.30 //

Others, having their food  regulated, offer the vital forces in the vital forces. All of them are knowers  of the sacrifice, whose sins are destroyed by sacrifice.

In the series of techniques  enumerated by Sri Krishna this is the last method. There are some, who through  systematic regulation of their diet, come to gain complete mastery over  themselves.

Those, who know the art of living  these techniques, weaken the functions of the organs of action and thereby  control their passions and appetites leading to purification of the mind and  destruction of sins for achieving the goal of Self-knowledge.

In the above mentioned twelve  different types of Yagna techniques self-effort is a common factor.  The yajnas are only the means to enable the  mind-intellect equipment to adjust itself better for meditation.  Meditation is the only path through which the  ego withdraws from false evaluation of itself for achieving spiritual growth.

yajnashishtaamritabhujo yaanti brahma sanaatanam
    naayam loko'styayajnasya kuto'nyah kurusattama  // 4.31 //

The eaters of the nectar - the  remnant of the sacrifice - go to the Eternal Brahman.  This world is not for the non-performer of  the sacrifice; how then the other world, O Best of the Kurus?

`Eating the nectar - the remnant  of the sacrifice' means the result of the above mentioned twelve types of  Yagnas. The result of performing any one of the above Yagnas is a greater  amount of self-control and the consequent inner integration of the individual  personality for the purpose of intense meditation. Such an integrated person  will have greater inner poise in his meditations through which he comes to  experience the Infinite and the Eternal indicated by the term `Brahman'.

Self-development and inner growth  cannot be had without sincere self-effort. Therefore, Sri Krishna exclaims how  one could hope to achieve the highest without sincere effort when even in this world  nothing great can be obtained without selfless and dedicated activity.

evam bahuvidhaa yajnaa vitataa brahmano mukhe
    karmajaan viddhi taan sarvaan evam jnaatwaa vimokshyase  // 4.32 //

Thus innumerable sacrifices  lie spread out before Brahman - literally at the mouth or face of Brahman -  Know them all as born of action and thus knowing, you shall be liberated.

When twelve different Yagnas  differing from one another have been described a doubt arises as to whether  these different paths lead to the same goal or produce different effects.  It is clarified here that all of them lead to  the same goal - innumerable sacrifices lie spread out before Brahman.

Another doubt as to the origin of  the theory of Yagnas is clarified by interpreting the same line of the verse to  mean the various Yagnas lie strewn about at the door of the Vedas giving  authenticity to the idea .

It is also urged that the paths  prescribed are to be achieved through self effort and hence the inevitability  of right action accomplished through the activities of the body, speech and  mind.

These activities cannot be  attributed to the Self as the Self is actionless. Thus if one realizes that  these are not my (Self) actions and I (Self) am actionless and detached he will  be freed from the worldly bondage.

As compared with these sacrifices  which are the means to attain inner integration, knowledge (considered as a  sacrifice) is being extolled in the next verse.