>>507890574actually im wrong about that. other context explains that the redemption is a monetary payment:
number 18
15“Every first issue of the womb of all flesh, whether man or animal, which they offer to the LORD, shall be yours; nevertheless the firstborn of man you shall surely redeem, and the firstborn of unclean animals you shall redeem. 16“As to their redemption price, from a month old you shall redeem them, by your valuation, five shekels in silver, according to the shekel of the sanctuary, which is twenty gerahs
but it seems that the levites were chosen in place of every firstborn son anyway
numbers3
11Again the LORD spoke to Moses, saying, 12“Behold, I have taken the Levites from among the children of Israel in place of every firstborn Israelite from the womb. The Levites belong to Me, 13for all the firstborn are Mine. On the day I struck down every firstborn in the land of Egypt, I consecrated to Myself all the firstborn in Israel, both man and beast. They are Mine; I am the LORD.”
what it comes down to is that its more complicated that your silly things about killing every firstborn son. next time do a bit more checking before presenting your new gottcha