Komentaryong Sumisipi para sa Mga Awit 105:36

ומת כל בכור, “and every firstborn will die.” The meaning is “regardless of whether he is the firstborn of the male (who provided the sperm) or if he is the firstborn of the female.” The curious wording in the Midrash Hagadol means that if one man impregnated 10 women all of whom had previously not given birth, the males born as a result are considered as “firstborn (of) the women.” If the situation is reversed, and a woman gives birth to ten males each by sperm of another male, then such “firstborn” are considered as “firstborn (of) men.” This is what Assaph means in Psalms 78,51: “He struck every firstborn in Egypt, the first fruits of their vigor in the tents of Cham.” We have another verse in Psalms 105,36 where the firstborn are also described as “the first fruit of their vigor.” It appears that the firstborn of “males” are described as ראשית לכל אונם, whereas the firstborn of women are described as ראשית אונים באהלי חם. The reason is that woman is traditionally associated with the word אהל, “tent.” Compare Judges 6,8 הם ומקניהם יעלו ואהליהם, “they and their cattle ascended together with their “tents,” i.e. with their women.