Charles Ellicott Commentary Exodus 12:23

"For Jehovah will pass through to smite the Egyptians; and when he seeth the blood upon the lintel, and on the two side-posts, Jehovah will pass over the door, and will not suffer the destroyer to come in unto your houses to smite you." — Exodus 12:23 (ASV)

The destroyer. —The “plague” of Exodus 12:13 is here called “the destroyer” (τὸν ὀλεθρεύοντα, Septuagint), as again in Hebrews 12:28. Jehovah seems to have employed an angel, or “angels” (Psalms 79:48) as His agents to effect the actual slaying of the firstborn. (Compare 2 Samuel 24:16; 1 Chronicles 21:15; 2 Kings 19:35.) There is no struggle or opposition (as Bishop Lowth and Redslob think) between Jehovah and “the destroyer,” who is simply His minister (Hebrews 1:14), commanded to enter some houses and to “pass over” others.