(Exodus, Ibid. 9) "And if to his son he designate her (as a wife)": He designates her to his son, but not to his brother. For it would follow (that he does designate her to his brother), viz.: If he designates his son, who does not take his place through yibum (levirate marriage), how much more so, his brother, who does take his place through yibum!—No, this may be true of his son, who takes his place vis-à-vis (reversion to his father of) a (field of) holding (on the Yovel), (as opposed to his brother, who does not.) It is, therefore, written "And if to his son he designate her"—to his son and not to his brother.