B.G 3.10, 11, 12, and 13

saha yajñāḥ prajāḥ sr̥ṣṭvā purōvāca prajāpatiḥ। anēna prasaviṣyadhvamēṣa vō'stviṣṭakāmadhuk ॥10॥

Previously, the lord of the beings created the beings together with Yajna and said "Prosper by means of Yajna. Let it fulfill your desired wishes."

dēvān bhāvayatā'nēna tē dēvā bhāvayantu vaḥ। parasparaṁ bhāvayantaḥ śrēyaḥ paramāvāpsyatha ॥11॥

Please the gods through Yajna, then those gods will please you. By such mutually benefitting activities, you will obtain the highest good.

iṣṭān bhōgān hi vō dēvā dāsyantē yajñabhāvitāḥ। tairdattānapradāyaibhyō yō bhuṅktē stēna ēva saḥ ॥12॥

The gods certainly grant wishes and objects of desire in the spirit of Yajna. The one who enjoys such given objects without offering them is certainly a thief.

yajñaśiṣṭāśinaḥ santō mucyantē sarvakilbiṣaiḥ। bhuñjatē tē tvaghaṁ pāpā yē pacantyātmakāraṇāt ॥13॥

The righteous who partake the remains of the 'Yajna' are freed from all defects. But, those who cook for selfish needs eat severe sins.

Gīta Bhāshya 3.13

tatra arthavādamāha - sahayajñā iti ॥10-13॥

Here 'artha-vada' is presented by stating 'sahayajñā' i.e. verses 10 to 13.

Note:
'artha-vada' is the term used to explain sentences that are meant to either praise the stated point of view, or to censure the opposing view.
As already clarified, 'Yajna' is an action done for the sake of the lord, without selfish motive, with equanimity. In this context, even demigods grant desires and wishes to the beings, as an offering to supreme lord, in the spirit of 'Yajna', i.e. anticipating the beings will perform 'Yajna' for their wellbeing. Not doing so amounts to misappropriation. Everyone must engage in the activities for the sake of the lord only as his service. Thus righteous activity undertaken becomes 'Yajna'. Activities undertaken with selfish motive are not 'Yajna', and results in bondage.