And it came to pass, when Pharaoh stubbornly refused to let us go, that Hashem killed kol bechor of Eretz Mitzrayim, both the bechor adam, and the bechor behemah; therefore Ani zovei'ach laHashem (I sacrifice to Hashem) kol that openeth the rechem (womb), being hazecharim (the males); but kol bechor of my banim I redeem.