Through erroneous judgement or cupidity or lust, O destroyer of enemies, a Brahmana takes a Shudra wife. He is not competent to take, according to the scriptures, such wife.
वैषम्यादथवा लोभात् कामाद् वापि परतंप। ब्राह्मणस्य भवेच्छूद्रा न तु दृष्टान्ततः स्मृता॥