Śrīmad-Bhāgavatam 1.12.35
Blended reading (Sanskrit + English inline)
Lord Śrī Kṛṣṇa was invited by Mahārāja Yudhiṣṭhira to look into the supervision of the performances of yajṣa, and the Lord, to abide by the orders of His elderly cousin, caused the performance of yajṣas by learned twice-born brāhmaṇas. Simply taking birth in the family of a brāhmaṇa does not make one qualified to perform yajṣas. One must be twice-born by proper training and initiation from the bona fide ācārya. The once-born scions of brāhmaṇa families are equal with the once-born śūdras, and such brahma-bandhus, or unqualified once-born scions, must be rejected for any purpose of religious or Vedic function. Lord Śrī Kṛṣṇa was entrusted to look after this arrangement, and perfect as He is, He caused the yajṣas to be performed by the bona fide twice-born brāhmaṇas for successful execution.
My note
Source: vedabase.io