Bava Basra, Chapter 8, Mishnah 2. Following the principles presented in the previous mishnah, the mishnah continues in the same direction and establishes: "Seder nachalos kach hu" - this is the hierarchy of the order of inheritance.
The source in the verse:
The mishnah quotes the verse from the section of the daughters of Tzelofchad, where the daughters receive an inheritance because they have no brothers: "Ish ki yamus uven ein lo, veha'avartem es nachalaso levito" - if a man dies and has no son, you shall pass his inheritance to his daughter. This is the basis for the rule that in the absence of sons, the daughter inherits.
From this verse, two expositions are also derived, which constitute fundamental rules of the laws of inheritance:
"Uven ein lo" - literally, that he has no son. The exposition reads it as: "uven ayen lo" - look and check if the son has living descendants. If the deceased's son has died, but the son's children - the deceased's grandchildren, and even his great-grandsons or granddaughters - are alive, they inherit before the deceased's daughters.
"Veha'avartem es nachalaso levito" - this is an awkward phrasing, and the Gemara derives from it that there is someone standing in line who is skipped over: "veha'avartem" - you transfer and skip. And who is this? This is the deceased's father, whose potential inheritance is skipped over and the inheritance is transferred to the deceased's daughter.
From here is the basis that in the absence of a daughter to inherit, meaning when the deceased has no living descendants at all, the direct heir is the deceased's father, as we learned in the previous mishnah. It is worth noting that the verses do not mention the father explicitly; they speak about the children and then about the descendants of the deceased's father, namely his brothers and sisters - but this is the source that the father precedes them.
The order of precedence in the words of the mishnah:
"Ben kodem labas" - the son receives precedence over the daughter.
"Vechol yotzei yerecho shel ben kodem labas" - all the descendants of the son (literally: those who emerge from his thigh) precede the deceased's daughter. The principle is that living descendants take the place of their deceased parent.
An example: The deceased had a son and a daughter, and the son died leaving behind a daughter. It turns out that there are two descendants - the deceased's granddaughter, the daughter of the son who died, and the deceased's daughter. The heir is the granddaughter, because she is of the "yotzei yerecho" of the son, a direct descendant of the son, and she precedes her aunt, the deceased's daughter.
Up to this point, the order of precedence is as follows:
The son, and any descendant of the son.
The daughter, and any descendant of the daughter.
The father.
The descendants of the father - the brothers and half-brothers.
"Bas kodemes la'achin" - the deceased's daughter precedes the deceased's brothers, who stand in fourth place.
"Yotzei yerecha shel bas kodemin la'achin" - the descendants of the daughter too, the grandsons and granddaughters on the daughter's side, precede the deceased's brothers.
"Achin kodemin la'achi ha'av" - the deceased's brothers precede his uncles, who are his father's brothers.
"Yotzei yerechan shel achin kodemin la'achi ha'av" - and similarly the descendants of the deceased's brothers, his nephews and nieces, precede his uncles.
"Zeh haklal":
"Kol hakodem lenachalah yotzei yereicho kodmin" - anyone who has priority in the order of inheritance, his living descendants will also have priority over any other relative, even if he himself has already passed away.
"Veha'av kodem lechol yotzei yereicho" - in every situation, the father has priority over his descendants.
In summary, the chain of inheritance: first the deceased and his children; if there are no children - the father of the deceased; if there is no father - the descendants of the father of the deceased; if there are none of these - his father's father, who also has priority over his descendants.