Those Brahmanas who know women in their season, or who never celebrate sacrifices, or whose families have no members well-read in the Vedas, are considered as Shudras in act.
उदक्यामासते ये च द्विजाः केचिदनग्नयः। होमं चाश्रोत्रियं येषां ते सर्वे पापकर्मिणः॥