Or HaChaim on Deuteronomy 21:16/אור החיים על דברים כ״א:ט״ז

1 הנחילו את בניו, את אשר יהיה לו, when he allocates the inheritance to the sons he has, etc. The Torah did not write ביום אשר הנחילו את אשר יהיה, לו את בניו, "on the day he allocates his inheritance to the ones who are his, i.e. his sons," which would have been far more appropriate, because the Torah wanted the word הנחילו to appear next to את בניו. This is an allusion to what we learned in Baba Batra 130 that a father may allocate to one of his sons [because he is his natural heir. Ed.] more than would be his share if all the children would inherit equally when no special allocation has been made.

2לא יוכל לבקר "He cannot give preference (the status of being the firstborn), etc." If he did so, he violates a negative commandment. This rule answers a question raised by Tossaphot in Baba Batra 130 which commences with the words תלמוד לומר לא יבכר.