This can be stated in active form. Alternate translation: "As Moses wrote" or "They did this because Moses wrote" (See: [[rc://en/ta/man/translate/figs-activepassive]])
"open the womb" here is an idiom that refers to the first baby coming out of the womb. This referred to both animals and people. Alternate translation: "Every firstborn offspring who is a male" or "Every firstborn son" (See: [[rc://en/ta/man/translate/figs-idiom]])