Bhagavad-Gita: Chapter 4, Verse 29

Rudra Vaisnava Sampradaya:

Visnuswami

Sridhara Swami's Commentary

Lord Krishna is explaining here that some offer the prana or outgoing breath as a yagna or offering of worship to the apana or incoming breath and the apana as a yagna to the prana continuous practice of this leads to both the prana and apana become an offering to kumbhaka which is the complete cessation of both breaths. When the breath is suspended all the vital forces merge into one and are controlled and the yagna is the merging of the senses into one. Others practice decreasing their food intake until it becomes minimal using it to offer as a yagna the senses which become greatly weakened due to lack of food. They follow the Vedic injunctions that the stomach should be half filled with food, a quarter filled with water and a quarter filled with air. Others meditate on the mystic sound of Hamsah meaning that I am and I am that in reference to the Supreme, for every breath inhaled meditating on ham as that I am and as every breathe exhaled meditating on sah as I am that. It is a known fact that to the extent that the mind becomes steady through continuous practice to that extent so does the breath, speech, body and the gaze become steady.

Brahma Vaisnava Sampradaya:

Madhvacarya

Madhvacarya's Commentary

Continuing Lord Krishna explains that others who are devoted to pranayama or regulation of the breath offer the prana or outgoing breath to the apana or incoming breath and the incoming breath to the outgoing breath. In this way they arrive at the stage of kumbhaka or complete restraint of the breath and this is considered to be yagna or offerings of worship.

Sri Vaisnava Sampradaya:

Ramanuja

Ramanuja's Commentary

Lord Krishna states that other yogis or those practising the science of the individual consciousness attaining communion with the ultimate consciousness; they devote themselves to pranayama or breath control consisting of three parts called rechaka or exhalation for 16 beats, puraka or inhaling for 32 beats and kumbhaka or cessation of breath for 64 beats. For every breath the prana or outgoing breath is offerred as yagna or worship into the apana or incoming breath and the apana is offered into the prana. These yogis require light diets and follow strict regimens of practice.

Kumara Vaisnava Sampradaya:

Nimbaditya

Kesava Kasmiri's Commentary

Lord Krishna now speaks of pranayama or breath control. Others offer the prana or exhalation into apana or inhaling breath and then again the apana into the prana. This is also considered as yagna or offerings of worship. How do they do this? It is done by the process of kumbhaka or the cessation of the breath between inhalation and exhalation. In this way they offer their every breath in yagna. In the next verse Lord Krishna tells about the rewards for those who perform such yagnas as mentioned above. Performing means they know the specific purpose for why and what they are performing such yagnas as well as how to perform it properly according to the Vedic saciptures and by doing so in this manner they have absolved their sins.