O King Pariksit, Lord Siva was pleased with Vasistha. Therefore, to satisfy him and to keep his own word to Parvati, Lord Siva said to that saintly person, "Your disciple Sudyumna may remain a male for one month and a female for the next"

Expressions researched:
"O King Parīkṣit, Lord Śiva was pleased with Vasiṣṭha. Therefore, to satisfy him and to keep his own word to Pārvatī, Lord Śiva said to that saintly person, "Your disciple Sudyumna may remain a male for one month and a female for the next. In this way he may rule the world as he likes"

Srimad-Bhagavatam

SB Canto 9

O King Parīkṣit, Lord Śiva was pleased with Vasiṣṭha. Therefore, to satisfy him and to keep his own word to Pārvatī, Lord Śiva said to that saintly person, "Your disciple Sudyumna may remain a male for one month and a female for the next. In this way he may rule the world as he likes."

SB 9.1.38-39, Translation and Purport

O King Parīkṣit, Lord Śiva was pleased with Vasiṣṭha. Therefore, to satisfy him and to keep his own word to Pārvatī, Lord Śiva said to that saintly person, "Your disciple Sudyumna may remain a male for one month and a female for the next. In this way he may rule the world as he likes."

The word gotrajaḥ is significant in this connection. Brāhmaṇas generally act as spiritual masters of two dynasties. One is their disciplic succession, and the other is the dynasty born of their semen. Both descendants belong to the same gotra, or dynasty. In the Vedic system we sometimes find that both brāhmaṇas and kṣatriyas and even vaiśyas come in the disciplic succession of the same ṛṣis. Because the gotra and dynasty are one, there is no difference between the disciples and the family born of the semen. The same system still prevails in Indian society, especially in regard to marriage, for which the gotra is calculated. Here the word gotrajaḥ refers to those born in the same dynasty, whether they be disciples or members of the family.