John Calvin on Exodus 4:17

17. And thou shalt take this rod. There is no doubt that God chose this shepherd’s rod to be the instrument of his power, in order the more to confound the pride of Pharaoh. For what but shame and reproach could it bring to Moses, that he should bear with him the crook with which he had heretofore guided his sheep in their folds and hovels? This symbol, then, of a rustic and contemptible occupation, was opposed to the scepter of Pharaoh, not without humiliation. In this respect, therefore, the obedience of Moses is worthy of praise, because he is not ashamed of a mean and humble appearance, but willingly carries his rod, and thus makes himself as nothing, and glorifies God. So is God usually wont to hide his treasures in earthen vessels, and to choose “the weak things of the world to confound the things that are mighty.” But from Moses being commanded to work the miracles with the rod, we gather that outward signs are often made use of by God, when He works by His own hand; not to derogate at all from his power, or to obscure his praise, but to make it manifest that the whole world is subject to him, and that he freely applies to whatever use he pleases, things which are otherwise of no account.

Exodus 4:18-23

18. And Moses went and returned to Jethro his father-in-law, and said unto him, Let me go, I pray thee, and return unto my brethren which are in Egypt, and see whether they be yet alive. And Jethro said to Moses, Go in peace.

18. Profectus est ergo Moses, et reversus est ad Jethro socerum suum: et dixit ad eum, Vadam nunc, et revertar ad fratres meos qui sunt in Aegypto, ut videam an adhuc ipsi vivant. Et dixit Jethro Mosi, Vade in pace.

19. And the Lord said unto Moses in Midian, Go, return into Egypt: for all the men are dead which sought thy life.

19. Dixerat autem Jehova ad Mosen in Midian, Vade, revertere in Aegyptum; quia mortui sunt omnes viri quaerebant animam tuam.

20. And Moses took his wife and his sons, and set them upon an ass, and he returned to the land of Egypt. And Moses took the rod of God in his hand.

20. Et accepit Moses uxorem suam, et filios suos, et sustulit eos super asinum: et reversus est in terram Aegypti. Et accepit Moses baculum Dei in manu sua.

21. And the Lord said unto Moses, When thou goest to return into Egypt, see that thou do all those wonders before Pharaoh which I have put in thine hand: but I will harden his heart, that he shall not let the people go.

21. Et ait Jehova ad Mosen, Quum profectus fueris, et reversus in Aegyptum, vide ut omnia signa quae posui in manu tua, facias illa coram Pharaone. Ego autem constringam cor illius, et non dimittet populum.

22. And thou shalt say unto Pharaoh, Thus saith the Lord, Israel is my son, even my first-born.

22. Et dices Pharaoni, Sic dicit Jehova, Filius meus, primogenitus meus Israel.

23. And I say unto thee, Let my son go, that he may serve me: and if thou refuse to let him go, behold, I will slay thy son, even thy first-born.

23. Ego autem jussi te dimittere filium meum ut mihi serviret: et renuisti dimittere eum. Ideo ecce ego occidam filium tuum, primogenitum tuum.