sa eva prathamam devah
kaumaram sargam asritah
cacara duscaram brahma
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
First of all, in the beginning of creation, there were the four unmarried sons of Brahma [the Kumaras], who, being situated in a vow of celibacy, underwent severe austerities for realization of the Absolute Truth.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The creation of the material world is effected, maintained and then again annihilated at certain intervals. So there are different names of the creations in terms of the particular types of Brahma, the father of the living beings in the creation. The Kumaras, as above mentioned, appeared in the Kaumara creation of the material world, and to teach us the process of Brahman realization, they underwent a severe type of disciplinary action as bachelors. These Kumaras are empowered incarnations. And before executing the severe type of disciplinary actions, all of them became qualified brahmanas. This example suggests that one must first acquire the qualifications of a brahmana, not simply by birth but also by quality, and then one can undergo the process of Brahman realization.