According to the law every man ought to marry; he must have a son who may one day pour for him the libations for the dead. Without sacrifice for the dead performed by a son, the soul of the father can never be liberated from a certain place in hell--from _Put_. The law distinguishes various kinds of marriage, and promises greater or less blessings to the descendants according as the marriage celebrated is of a more or less holy kind. The son born of the better kinds of marriage can purify a larger number of the members of the family upwards and downwards, _i.e._ of those already dead and those still to be born. If a father gives his daughter, bathed and adorned, to a husband learned in writing whom he has honourably invited and received into his house, the marriage is a Brahman-marriage. The son born of such a wife purifies ten members upwards and downwards both on the father's and the mother's side. When the father gives his daughter to the priest at the sacrifice it is a divine marriage; the son purifies seven members upwards and downwards on either side. If the father gives the daughter to the bridegroom with the words: "Fulfil ye all duties which devolve on you;" it is a _prajapati_ marriage, and the son purifies six members upwards and downwards. If the bridegroom has given a pair of cattle (a bull and cow) for religious objects, the marriage of the Rishis is celebrated; the son purifies three members upwards and downwards. These are the good forms of marriage, the four which follow are bad. Marriage from mutual inclination on either side is the marriage of the heavenly musicians, the Gandharvas. If the father has sold his daughter or taken gifts for her, it is the marriage of the Asuras, or evil spirits. Still worse is the marriage by abduction--the marriage of the Rakshasas; and the worst form of all is when the bride is previously intoxicated by drugs. This is the marriage of the blood-suckers (Piçacha). These kinds of marriages have no expiatory power for the ancestors or descendants; none but cruel, lying, and Veda-despising sons can spring from them.[317] To these rules on the form of marriage the law adds that the younger sister is not to be married before the elder--nor can the younger brother marry before the elder--and advises that a wife be not taken from families too nearly related, such as those belonging to the same tribe (_gotra_); or from those which neglect the sacred rites, or those in which diseases prevail. A girl of eight years old is suitable for a husband of twenty-four; a girl of twelve for a husband of thirty. The later collections of laws repeat the rule that marriages are not to be celebrated with families which invoke the same ancestors.[318]