Or HaChaim on Exodus 4:17/אור החיים על שמות ד׳:י״ז

1 ואת המטה הזה תקח בידך, "and take this staff in your hand, etc." According to the Zohar section 3 page 28 there were two staffs. The Torah then spoke about "this one" to tell Moses that he should not take the other staff.

2The expression "take in your hand" means "permanently;" The reason was that this staff should be a mark of distinction, something not unlike present-day rulers who carry a mace with them as a sign of their constitutional right to legislate. Moses took the "staff of G'd" with him as mentioned in verse 20 as a memento of this conversation and as a sign of his authority. G'd had said: "take it in your hand" so that we should not interpret that Moses took his staff like ordinary people take a walking-cane.

3אשר תעשה בו את האותות, "the one with which you will perform the miracles." This may be a reference to the staff with which Aaron performed such miracles as turning it into a snake (7,10). According to the Zohar we have just quoted that staff became known as "the staff of Aaron;" G'd had commanded Aaron also to have his staff ready at all times. According to Targum Yonathan 2,21 the staff was made of sapphire and no one was able to even move it except Moses. Accordingly, the very fact that Moses could "take" it was a miracle in itself. The words וזה לך האות therefore meant that no one but Moses would be able to handle the staff.