B.G 4.31
yajñaśiṣṭāmr̥tabhujo yānti brahma sanātanam। nāyaṁ loko'styayajñasya kuto'nyaḥ kurusattama ॥31॥
Those enjoy the remnents of the Yajna attain that eternal supreme Brahman. O Arjuna, This world is not for those non performers of Yajna, much less the other.
Gīta Tātparya 4.31
All internal (mental) and external forms of Yajna are ultimately worship of lord Vishnu only. It is He who grants results.
tatpūjātvena indriyādisaṁyamaṁ kurvanti। yajñe naiva iti sarvatrāpi anvīyate।
By worship of the supreme Brahman only control over senses and other faculties is obtained. (The worship is performed) through Yajna, not without, is the implied meaning everywhere.
"tenaiva taṁ pūjayedvā vihitairvā'nyasādhanaiḥ। sa eva viṣṇoryajñaḥ syāt mānaso vātha bāhyakaḥ॥"
iti brahmavaivarte॥31॥
"He may worship Him alone with prescribed means as there is no other path. He alone, the lord Vishnu, is the Yajna, whether it is mental or external."
-states Brahma Vaivarta Purana.