Exodus 12:23

23.For the Lord will pass through. He forbids them to go out during the night, lest they should mix themselves with the Egyptians, but commands them to keep quietly under the protection of the blood. By this sign they were admonished that they also were exposed to destruction, if they did not separate themselves from the unbelievers under the safeguard of the blood. Afterwards the promise: is added, that, provided this were done, the angel would pass them over, and inflict no injury upon them, because God would acknowledge the houses so marked as His own. Wherefore, it is again repeated, that they should alone be safe by the blessing of the blood, who should not neglect to sprinkle themselves with it; because faith alone confers upon us the salvation which is obtained by the slaughter of the victim. The angel, whom God had delegated for afflicting Egypt, is here undoubtedly called “the destroyer;” and, although He often executes His judgments by evil angels, it is to be gathered from other passages that this was one of the elect angels, who also was the minister of the people’s deliverance under Christ as the Head.