Kardama Muni was ordered by his father, Prajāpati, to produce children. In the beginning of creation the Prajāpatis were meant to produce the large population which was to reside in the planets of the gigantic universe. But Kardama Muni said that although his father was Prajāpati, who desired him to produce children, actually his origin was the Supreme Personality of Godhead, Viṣṇu, because Viṣṇu is the origin of everything; He is the actual creator of this universe, He is the actual maintainer, and when everything is annihilated, it rests in Him only. That is the conclusion of Śrīmad-Bhāgavatam. For creation, maintenance and annihilation there are the three deities Brahmā, Viṣṇu and Maheśvara (Śiva), but Brahmā and Maheśvara are qualitative expansions of Viṣṇu. Viṣṇu is the central figure. Viṣṇu, therefore, takes charge of maintenance. No one can maintain the whole creation but He. There are innumerable entities, and they have innumerable demands; no one but Viṣṇu can fulfill the innumerable demands of all the innumerable living entities. Brahmā is ordered to create, and Śiva is ordered to annihilate. The middle function, maintenance, is taken charge of by Viṣṇu. Kardama Muni knew very well, by his power in progressive spiritual life, that Viṣṇu, the Personality of Godhead, was his worshipable Deity. Whatever Viṣṇu desired was his duty, and nothing else. He was not prepared to beget a number of children. He would beget only one child, who would help the mission of Viṣṇu. As stated in Bhagavad-gītā, whenever there is a discrepancy in the discharge of religious principles, the Lord descends on the surface of the earth to protect religious principles and to annihilate the miscreants.
Marrying and begetting a child is considered to liquidate one's debts to the family in which one is born. There are many debts which are imposed upon a child just after his birth. There are debts to the family in which one is born, debts to the demigods, debts to the Pitās, debts to the ṛṣis, etc. But if someone engages only in the service of the Supreme Lord, the Personality of Godhead, who is actually worshipable, then even without trying to liquidate other debts, one becomes free from all obligations. Kardama Muni preferred to devote his life as a servant of the Lord in paramahaṁsa knowledge and to beget a child only for that purpose, not to beget numberless children to fill up the vacancies in the universe.