Srimad-Bhagavatam: Canto 1 - Chapter 1 - Verse 12
कर्मण्यस्मिन्ननाश्वासे धूमधूम्रात्मनां भवान् ।आपाययति गोविन्दपादपद्मासवं मधु ॥ १२ ॥
karmaṇy asminn anāśvāsedhūma-dhūmrātmanāṁ bhavānāpāyayati govinda-pāda-padmāsavaṁ madhu
We have just begun the performance of this fruitive activity, a sacrificial fire, without certainty of its result due to the many imperfections in our action. Our bodies have become black from the smoke, but we are factually pleased by the nectar of the lotus feet of the Personality of Godhead, Govinda, which you are distributing.
The sacrificial fire kindled by the sages of Naimiṣāraṇya was certainly full of smoke and doubts because of so many flaws. The first flaw is that there is an acute scarcity of expert brāhmaṇas able to carry out such performances successfully in this Age of Kali. Any discrepancy in such sacrifices spoils the whole show, and the result is uncertain, like agricultural enterprises. The good result of tilling the paddy field depends on providential rain, and therefore the result is uncertain. Similarly, performance of any kind of sacrifice in this Age of Kali is also uncertain. Unscrupulous greedy brāhmaṇas of the Age of Kali induce the innocent public to such uncertain sacrificial shows without disclosing the scriptural injunction that in the Age of Kali there is no fruitful sacrificial performance but the sacrifice of the congregational chanting of the holy name of the Lord. Sūta Gosvāmī was narrating the transcendental activities of the Lord before the congregation of sages, and they were factually perceiving the result of hearing these transcendental activities. One can feel this practically, as one can feel the result of eating food. Spiritual realization acts in that way. The sages of Naimiṣāraṇya were practically sufferers from the smoke of a sacrificial fire and were doubtful about the result, but by hearing from a realized person like Sūta Gosvāmī, they were fully satisfied. In the Brahma-vaivarta Purāṇa, Viṣṇu tells Śiva that in the Age of Kali, men full of anxieties of various kinds can vainly labor in fruitive activity and philosophical speculations, but when they are engaged in devotional service, the result is sure and certain, and there is no loss of energy. In other words, nothing performed for spiritual realization or for material benefit can be successful without the devotional service to the Lord.