Mbh 13.49.1a

"'Bhishma said, "A person that is born of an irregular union presents diverse features of disposition. One's purity of birth, again, is to be ascertained from one's acts which must resemble the acts of those who are admittedly good and righteous. A disrespectable behaviour, acts opposed to those laid down in the scriptures, crookedness and cruelty, and abstention from sacrifices and other spiritual acts that lead to merit, proclaim one's impurity of origin. A son receives the disposition of either the sire or the mother. Sometimes he catches the dispositions of both. A person of impure birth can never succeed in concealing his true disposition. As the cub of a tiger or a leopard resembles its sire and dam in form and in (the matter of) its stripes of spots, even so a person cannot but betray the circumstance of his origin. However covered may the course of one's descent be, if that descent happens to be impure, its character or disposition is sure to manifest itself slightly or largely. A person may, for purposes of his own, choose to tread on an insincere path, displaying such conduct as seems to be righteous. His own disposition, however, in the matter of those acts that he does, always proclaims whether he belongs to a good order or to a different one. Creatures in the world are endued with diverse kinds of disposition. They are, again, seen to be employed in diverse kinds of acts. Amongst creatures thus employed, there is nothing that is so good or precious as pure birth and righteous conduct. If a person be born in a low order, that good understanding which arises from a study of the scriptures fails to rescue his body from low acts. Absolute goodness of understanding may be of different degrees. It may be high, middling, or low. Even if it appears in a person of low extraction, it disappears like autumnal clouds without producing any consequences.