Matthew Poole and continuators on Exodus 12:29

29 And it came to pass, that at midnight the LORD smote all the first-born in the land of Egypt, from the first-born of Pharaoh that sate on his throne, unto the first-born of the captive that was in the dungeon, and all the first-born of cattle.

A great aggravation of the Plague: For then darkness it self strikes men with horrour and makes any calamity more terrible, then they were asleep and secure and least expected such a stroke.

Both of man and beast, whether Male or Female. Some extend it to all that were first-born, and so many persons might be killed in one house, as both Father and Mother, and several Sons, which might be the first-born by several Mothers, and Sons sons or Daughters, &c. Others confine it to the first-born Child in the Family. I conceive the heads of the Family are not included, for these though they might be the first-born Children of their Parents Families, yet were not nor ever are called or accounted the first-born of their own Families, but the heads and roots of them: But for all the rest I conceive they are all included, because all such were really first-born and did first open their mothers Womb, and all such were to be set apart unto the Lord, instead of these first-born of the Egyptians now slain, chap. 13. 12, 15. and therefore are in both places to be understood in the same latitude.

Marginal references: chap. 11. 4.; Numb. 8. 17. and 33. 4. Psal. 78. 51. and 105. 36. and 135. 8. & 136. 10.; Wisd. 18. 11. chap. 4. 23.; Heb. house of the pit.