Nanda Mahārāja and Yaśodā were also living in Mathurā because Kṛṣṇa and Balarāma were there, but after some time they wanted to go back to Vṛndāvana. Kṛṣṇa and Balarāma went before Nanda and Yaśodā and very affectionately embraced them, and then the two Lords spoke as follows: “Dear father and mother, although We were born of Vasudeva and Devakī, you have been Our real father and mother, because from Our very birth and childhood you raised Us with great affection and love. Your affectionate love for Us was more than anyone can offer one’s own children. You are actually Our father and mother, because you raised Us as your own children when We were just like orphans. For certain reasons We were rejected by Our father and mother, and you protected Us. Dear father and mother, We know that you will feel separation upon returning to Vṛndāvana and leaving Us here, but please rest assured that We shall come back to Vṛndāvana just after giving some satisfaction to Our real father and mother, Vasudeva and Devakī, and Our grandfather and other family members.” Kṛṣṇa and Balarāma thus satisfied Nanda and Yaśodā by sweet words and by presentations of various kinds of clothing, ornaments and copper utensils. They satisfied them, along with their friends and neighbors who had come with them from Vṛndāvana to Mathurā, as fully as possible. On account of excessive parental affection for Balarāma and Kṛṣṇa, Nanda Mahārāja felt tears in his eyes, and he embraced Them and started with the cowherd men for Vṛndāvana.
After this, Vasudeva had his sons initiated by sacred thread as the token of second birth, which is essential for the higher castes of human society. Vasudeva called for his family priest and learned brāhmaṇas, and the sacred thread ceremony of Kṛṣṇa and Balarāma was duly performed. During this ceremony, Vasudeva gave various ornaments in charity to the brāhmaṇas and endowed them with cows decorated with silken cloths and golden ornaments. Then Vasudeva remembered the cows he had wanted to give in charity to the brāhmaṇas after the birth of Kṛṣṇa and Balarāma. But being imprisoned by Kaṁsa at that time, Vasudeva had been able to do so only within his mind, for Kaṁsa had stolen all his cows. With the death of Kaṁsa his cows were released, and now Vasudeva gave the actual cows to the brāhmaṇas. Then Balarāma and Kṛṣṇa were duly initiated with the sacred thread ceremony, and They repeated the chanting of the Gāyatrī mantra. The Gāyatrī mantra is offered to disciples after the sacred thread ceremony, and Balarāma and Kṛṣṇa properly discharged the duties of chanting this mantra. Anyone who executes the chanting of this mantra has to abide by certain principles and vows. Although Balarāma and Kṛṣṇa are transcendental personalities, They strictly followed the regulative principles. They were initiated by Their family priest, Gargācārya, usually known as Garga Muni, the ācārya of the Yadu dynasty. According to Vedic culture, every respectable family has an ācārya, or spiritual master. One is not considered a perfectly cultured man without being initiated and trained by an ācārya. It is said, therefore, that one who has approached an ācārya is actually in perfect knowledge. Lord Kṛṣṇa and Lord Balarāma are the Supreme Personality of Godhead, the master of all education and knowledge. There was no need for Them to accept a spiritual master, or ācārya, yet for the instruction of ordinary men They also accepted a spiritual master for advancement in spiritual knowledge.
It is customary, after being initiated in the Gāyatrī mantra, for one to live away from home for some time under the care of the ācārya, to be trained in spiritual life. During this period, one has to work under the spiritual master as an ordinary menial servant. There are many rules and regulations for a brahmacārī living under the care of an ācārya, and Kṛṣṇa and Balarāma strictly followed those regulative principles while living under the instruction of their spiritual master, Sāndīpani Muni, who was a resident of Avantīpura, in the northern Indian district of Ujjain. According to scriptural injunctions, a spiritual master should be respected and regarded on an equal level with the Supreme Personality of Godhead. Kṛṣṇa and Balarāma exactly followed those principles with great devotion and underwent the regulations of brahmacarya. Thus They satisfied Their spiritual master, who instructed Them in Vedic knowledge. Being very satisfied, Sāndīpani Muni instructed Them in all the intricacies of Vedic wisdom and in supplementary literature such as the Upaniṣads. Because Kṛṣṇa and Balarāma happened to be kṣatriyas, They were specifically trained in military science, politics and ethics. Politics includes such departments of knowledge as how to make peace, how to fight, how to pacify, how to divide and rule and how to give shelter. All these items were fully explained and instructed to Kṛṣṇa and Balarāma.