Srimad Bhagvata Mahapurana: Book 5: Chapter 3: Verses 1-9
Sri Suka began again : Desirous of obtaining progeny, king Nabhi alongwith (his wife) queen Merudevi, who had no issue, worshipped with a concentrated mind Lord Visnu (the Deity presiding over sacrifices). The Lord, who possessed of a (most) charming personality, is difficult to attain even when (all) the means (of propitiating Him)-such as the materials, place and time (of worship), the prayers (muttered in the course of worship), the priests conducting the worship, the fees paid to them and (the due observance of) the procedure (laid down for the worship)-are fully employed. Yet, while Nabhi was (thus) reverently (engaged in) worshipping Him with a pure (devout) heart and while the rites known by the name of Pravargya (which serve as a prelude to the performance of a Soma sacrifice) were proceeding, the heart of the Lord was seized with a longing to accomplish the desired object of His servant because of His affection for His devotees, and He revealed before him His most independent captivating form, which ravished the soul by its limbs, which were (individually most) pleasing to the mind and eyes.
The Lord actually appeared with two pairs of arms, was clad in tawny silk and had the splendid Srivatsa mark on His bosom. He was distinguished by His peerless conch, lotus, wreath of sylvan flowers, discus, the Kaustubha gem, mace and so on and adorned with a crown, ear-rings, bracelets, girdle, necklace, armlets, anklets and other (such) ornaments of the body, all made of radiant jewels. Seeing the all-effulgent Supreme Person, the priests officiating at the sacrifice as well as the directors of the sacrifice and the sacrificer (himself) waited upon Him, their heads bent low, with water to wash His hands with (as a mark of respect), receiving Him with the same high regard as penniless people would receive a rich treasure. The priests said : (Though self-perfect in everyway,) be pleased, O most adorable One, to accept again and again (by Your own grace) the homage offered by us, Your servants. (Incapable of extolling You,) we have been taught by worthy souls only to repeat the word 'Namah' (Obeisance to You). (As a matter of fact,) what man whose mind is engrossed in the phenomenal world (which is a modification of the modes of Prakrti) and who is (therefore) powerless can hope to determine Your essential character with the help of the names and colours and forms of this material universe (which cannot even touch the fringe of Your being)-You who are the Supreme Lord transcending (both) Prakrti (Matter) and Purusa (Spirit). The utmost he can do is to recount a part of Your multitudinous excellent virtues, which drive away the sins of all mankind and are most auspicious (by nature). On the other hand, O Supreme One, You are propitiated in everyway through worship offered even with prayers lovingly uttered by your servants in a faltering voice, water, undefiled young leaves, (particularly) leaves of the holy basil plant and sprouts of panic grass.
Otherwise we do not perceive any gain worth the name to You even through this sacrifice-cumbrous with elaborate details-(being carried on) here inasmuch as You are the very embodiment of all the (four) objects of human pursuit perennially and directly flowing in an abundant degree from Your own Self and not conflicting with each other. In our case, however, who seek blessing (of various kinds), 0 Lord, this (sacrifice) should only prove to be a means of propitiating You (and thereby fetching the desired boon). That is why, out of abundant compassion for us, ignorant as we are of our highest good, O Supreme Person, who are greater than the greatest. You have appeared here of Your own accord, like one expecting homage, with intent to reveal to us Your own glory known by the name of final beatitude as well as to bestow (on us) our desired blessings-even though You have not been (properly) worshipped-just as a sage would approach ignorant people of his own accord.