Ramban on Shemos 4:21

English: AND THE ETERNAL SAID UNTO MOSES: ‘WHEN THOU GOEST BACK INTO EGYPT SEE ALL THE WONDERS,’ etc. Rabbi Abraham ibn Ezra said that this was said to Moshe when he was yet in Midian. Hashem informed him that He would harden Pharaoh’s heart and he would not let the people go because of all the wonders which he would see until the last wonder. Ibn Ezra’s intent is thus to explain this verse as saying: “ See that for all the wonders which I have put in thy hand and which you will do before Pharaoh , for all of these he will not let them go until you will tell him that I will slay his son, his firstborn. Then he will let them go.” This explanation is not correct for what sense is there for the expression, when thou goest back into Egypt, see , etc.? Rather, the purport thereof is as follows: When leaving Midian, Moshe took the rod of Hashem in his hand 306 Verse 20. to mark the way with his footsteps . 307 Psalms 85:14. Hashem forewarned him and said to him, “When you go on the way, mark well and behold 308 Ezekiel 44:5. that all the wonders which I have put in your hand you should do before Pharaoh; do not forget to do anything before him. And I will harden his heart , but do not despair from doing t