Charles Ellicott Commentary Exodus 11:1

"And Jehovah said unto Moses, Yet one plague more will I bring upon Pharaoh, and upon Egypt; afterwards he will let you go hence: when he shall let you go, he shall surely thrust you out hence altogether." — Exodus 11:1 (ASV)

And the Lord said. —Rather, Now the Lord had said. The passage (Exodus 11:1–3) is parenthetic, and refers to a revelation made to Moses before his present interview with Pharaoh began. The insertion is needed in order to explain the confidence of Moses in regard to the last plague (Exodus 11:5), and the effect it would have on the Egyptians (Exodus 11:8).

When he shall let you go, he shall surely thrust you out hence altogether. —The word rendered “altogether” belongs to the first clause. Translate, when he shall let you go altogether, he shall assuredly thrust you out hence.