I (the Supreme) am the kratu (a Vedic rite), I am the yajña (the smritis prescribe). I am the offering to departed souls, and all the herbs and medicinal plants. I am mantra (the invocational word) as well as the ghee offered to sacrificial fire. I am the fire into which oblations are made, as also the materials offered to sacrificial fire.
Krishna shows how the Supreme is manifest as all constituents of the world, all one uses in his life. Yajμa denotes Vedic and allied sacrifices. But Krishna covers under yajμa the whole variety of religio-devotional pursuits, with or without materials (4.29-33).
He also includes all materials offered to departed souls, although they form a different category. All herbs and medicinal plants are also the Supreme’s manifestation.
Sounds and words uttered in religious performances, including prayers and praises, are invocations. Krishna sums up everything and all – yajμas (sacrifices) including the fire in the ceremonial altar, the ghee (purified butter) and all the items poured as oblation – as the Supreme itself!