Bava Batra

and, secondly,  [one should follow the order of the Torah,] as it is written, If a man die and have no son?  — The Tanna prefers  [to begin with the case of a father who is heir to his son] because this [law] has been arrived at through an exposition. What is the exposition? — It has been taught: His kinsman,  refers to the [dead man's] father. This teaches that a father takes precedence  over brothers. One might [assume] that he also takes precedence over a son, [therefore] it was expressly stated, that is next [to him],  [which implies] he who is nearest  takes precedence. What reason is there  for including the son  and excluding the brother? — The son is included because, as is known,  he is [entitled] to take his father's place in designating [the Hebrew handmaid of his father to be his wife],  and [also in the redeeming] of a field of [his father's] possession.  On the contrary! [Rather say:] 'The brother is included because he also takes the place of his brother in the case of a levirate marriage.'  Surely levirate marriage only takes place where there is no son, but where there is a son there is no levirate marriage. [From what has been said it appears] that the [only] reason [for the precedence of a son is] that there is this reply,  but had it not [been] so, it would have been held [that] a brother takes precedence, [but cannot] this [law]  be deduced