B.G 4.31

यज्ञशिष्टामृतभुजो यान्ति ब्रह्म सनातनम्। नायं लोकोऽस्त्ययज्ञस्य कुतोऽन्यः कुरुसत्तम ॥३१॥

yajñaśiṣṭāmr̥tabhujo yānti brahma sanātanam। nāyaṁ loko'styayajñasya kuto'nyaḥ kurusattama ॥31॥

[यज्ञ शिष्ट अमृत भुजो यान्ति ब्रह्म सनातनम्। न अयं लोकः अस्ति अयज्ञस्य कुतः अन्यः कुरु-सत्-तम॥
yajña śiṣṭa = the remnents of the Yajna; amr̥ta bhujo = enjoyed the nector of; yānti = attain; brahma = Brahman, the supreme lord; sanātanam = eternal;। na = not; ayaṁ = this; lokaḥ = world; asti = exists; ayajñasya = for non performer of Yajna; kutaḥ = from where; anyaḥ = others; kuru -sat-tama = doer of good deeds;]

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.

तत्पूजात्वेन इन्द्रियादिसंयमं कुर्वन्ति। यज्ञे नैव इति सर्वत्रापि अन्वीयते।

tatpūjātvena indriyādisaṁyamaṁ kurvanti। yajñe naiva iti sarvatrāpi anvīyate।

[tatpūjātvena = by worship of Him; indriyādisaṁyamaṁ = control of the senses; kurvanti = is performed;। yajñe = in Yajna; naiva = not without; iti = thus; sarvatrāpi = everywhere; anvīyate = applies;।]

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.

"तेनैव तं पूजयेद्वा विहितैर्वाऽन्यसाधनैः। स एव विष्णोर्यज्ञः स्यात् मानसो वाथ बाह्यकः॥"

इति ब्रह्मवैवर्ते॥३१॥

"tenaiva taṁ pūjayedvā vihitairvā'nyasādhanaiḥ। sa eva viṣṇoryajñaḥ syāt mānaso vātha bāhyakaḥ॥"

iti brahmavaivarte॥31॥

["tenaiva = by Him alone; taṁ = Him; pūjayedvā = is worshiped; vihitairvā'nyasādhanaiḥ = is the prescribed means, there is no other path;। sa eva = He alone; viṣṇoryajñaḥ = lord Vishnu, is Yajna; syāt = may be; mānaso = in the mind; vātha = or otherwise; bāhyakaḥ = external;]

[iti brahmavaivarte = states Brahma Vaivarta Purana;]

"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.