Parallel
Exodus 13:15
Brenton's English Septuagint · Berean Standard Bible
And when Pharao hardened [his heart so as not] to send us away, he slew every first-born in the land of Egypt, both the first-born of man and the first-born of beast; therefore do I sacrifice every [offspring] that opens the womb, the males to the Lord, and every first-born of my sons I will redeem.
And when Pharaoh stubbornly refused to let us go, the LORD killed every firstborn in the land of Egypt, both of man and beast. This is why I sacrifice to the LORD the firstborn male of every womb, but I redeem all the firstborn of my sons.’