Jaiminīya Upaniṣad Brāhmaṇa 3.6.7

3.6.7

agnir ha vā abandhur bandhumat sāma
kasmād vā hy enaṃ dārvoḥ kasmād vā paryāvṛtya manthanti sa śraiṣṭhyāyādhipatyāyānnādyāya purodhāyai jāyate /

Agni indeed is the sāman having relatives though having no relative.
For why, turning it round and round, do they churn him from two pieces of wood? He is born for pre-eminence, overlordship, abundance of food, and priesthood.