Bhagavad Gita 17.11अफलाकाङ्क्षिभिर्यज्ञो विधिदृष्टो य इज्यते।यष्टव्यमेवेति मनः समाधाय स सात्त्विकः ॥

When a sacrifice is done with all due Sattvic rites, faith and devotion, without the least taint of desire for reward, with the mind fixed on the sacrifice only, for its own sake (for the,sake of discharging the duty only), then it is said to be pure in its nature. Here the sacrifice is done in a disinterested spirit or with an attitude of desirelessness (Nishkamya Bhava) as an auxiliary to the attainment of the knowledge of the Self. Such selfless and desireless actions purify the mind and prepare the aspirant for the reception of divine light or knowledge of the Self. The Sattvic nature of a man forces him to do such selfless and desireless sacrifices. He does not care even for his own emancipation. He performs them with the firm belief that they ought to be done. He does them with the firm resolve that sacrifice is a duty.Yajna here is not limited to the ceremonial sacrifice. It is used in a broad sense. Any unselfish action done without attachment, without agency or egoism and without expectation of reward, as an offering unto the Lord, is a Yajna or sacrifice.