Śāstra means, as I have already told you, the orders of Kṛṣṇa or orders of God. Sādhu-śāstra-guru. They are the same thing. There is no difference. A sādhu follows the orders of the scriptures. A guru follows the order of the scriptures. And śāstra is description of the Supreme Lord. Just like we are reading Bhagavad-gītā. These are the injunction of Kṛṣṇa. Therefore it is śāstra. Or anyone who writes in terms of the śāstra, that is right direction. If we speak Bhagavad-gītā as Kṛṣṇa desires, then it is right. And if we describe Bhagavad-gītā to fulfil our ulterior motives for some purpose, then it is useless.
So similarly, Kṛṣṇa said, dharmāviruddho bhūteṣu kāmo 'smi bharatarṣabha. Those who are not following the principles how to beget child, or not observing the garbhādhāna-saṁskāra, according to śāstra, immediately the family becomes converted into śūdra. No more brāhmiṇ, no more kṣatriya, if he does not follow. This is very easy to understand. If you do something illegally, against the law, immediately you become a criminal. Similarly, dharmāviruddha. The garbhādhāna-saṁskāra has to be observed. Otherwise we become śūdra, no more brāhmiṇ, no more kṣatriya.
So it is very difficult to say at the present moment whether garbhādhāna-saṁskāra is observed. At least, in garbhādhāna-saṁskāra we understand that "This child is born of a real brāhmiṇ." But without garbhādhāna-saṁskāra, who knows how the child is born? Nobody knows except the mother. Therefore the śāstra says, "In this age, Kali-yuga, because this garbhādhāna-saṁskāra is not observed regularly," kalau śūdrāḥ sambhavāḥ, "everyone in the Kali-yuga is a śūdra, because the garbhādhāna-saṁskāra is not observed."
Of course, those who are observing . . . but it is very hard to say who is observing. But if it is not observed, then any child born, either in the brāhmiṇ family or kṣatriya family or vaiśya family, because the garbhādhāna-saṁskāra is not observed, it is to be understood that that child is śūdra.
Even if the garbhādhāna-saṁskāra is observed, still, by birth, it is accepted that every child is a śūdra. Janmanā jāyate śūdraḥ saṁskārād bhaved dvijaḥ. And if the regulative purificatory processes are adopted, then he becomes dvija. Dvija means twice-born. First-born by the father and mother, and his second birth is by the spiritual master and Vedic knowledge. Veda-mātā. Vedic knowledge and the spiritual master gives another birth. Upanayana-saṁskāra.
Upanayana. Upanayana, means coming nearer to the understanding of Vedic knowledge, upanayana, or coming nearer to the spiritual master. Then he begins studying of Vedas. Veda-pāṭhād bhaved vipraḥ. When he has studied nicely Vedas, then he becomes a vipra. And when he understands the Supreme Lord or the Para-brahman, then he is brāhmiṇ. This is the process.