All this is to be done only when the caste of the son's true mother cannot be learnt. Among sons, he who is born of a maiden and he who is born of a mother who had conceived before her marriage but brought nim forth subsequent to that act, are considered as very disgraceful and degraded.
संस्कर्तुं वर्गगोत्रं च मातृवर्णविनिश्चये। कानीनाध्यूढजौ वापि विज्ञेयौ पुत्र किल्बिषौ॥