Before the advent of Lord Kṛṣṇa within this universe, there were many battles between the demons and the demigods. Many demons died in the fighting, and they all were given the chance to take birth in high royal families on this earth. Because of their royal exalted posts, all these demons became very much puffed up, and their only business was to harass their subjects. Lord Kṛṣṇa appeared on this planet just at the end of Dvāpara-yuga to annihilate all these demoniac kings. As it is said in the Bhagavad-gītā, paritrāṇāya sādhūnāṁ vināśāya ca duṣkṛtām: (BG 4.8) "The Lord comes to protect the devotees and annihilate the miscreants." Some of the demigods were asked to appear on this earth to assist in the transcendental pastimes of Lord Kṛṣṇa. When Kṛṣṇa appeared, He came in the association of His eternal servitors, but some of the demigods also were requested to come down to assist Him, and thus they took their births in the Yadu dynasty. The Yadu dynasty had 101 clans in different parts of the country. All the members of these different clans respected Lord Kṛṣṇa in a manner befitting His divine position, and all of them were His devotees heart and soul. Thus all the members of the Yadu dynasty were very opulent, happy and prosperous, and they had no anxieties. Because of their implicit faith in and devotion to Lord Kṛṣṇa, they were never defeated by any other kings. Their love for Kṛṣṇa was so intense that in their regular activities—in sitting, sleeping, traveling, talking, sporting, cleansing, bathing—they were simply absorbed in thoughts of Kṛṣṇa and paid no attention to bodily necessities. That is the symptom of a pure devotee of Lord Kṛṣṇa. Just as when a man is fully absorbed in some particular thought he sometimes forgets his other bodily activities, the members of the Yadu dynasty acted automatically for their bodily necessities, but their actual attention was always fixed on Kṛṣṇa. Their bodily activities were performed mechanically, but their minds were always absorbed in Kṛṣṇa consciousness.
Śrīla Śukadeva Gosvāmī has concluded the Ninetieth Chapter of the Tenth Canto of Śrīmad-Bhāgavatam by pointing out five particular excellences of Lord Kṛṣṇa. The first excellence is that before Lord Kṛṣṇa's appearance in the Yadu family, the river Ganges was known as the purest of all things; even impure things could be purified simply by touching the water of the Ganges. This superexcellent power of the Ganges water was due to its having emanated from the toe of Lord Viṣṇu. But when Lord Kṛṣṇa, the Supreme Viṣṇu, appeared in the family of the Yadu dynasty, He traveled personally throughout the kingdom of the Yadus, and by His intimate association with the Yadu dynasty, the whole family not only became very famous but also became more effective in purifying others than the water of the Ganges.