Exodus 17:5

עבר לפני העם PASS BEFORE THE PEOPLE and see whether they will stone you! (Midrash Tanchuma, Beshalach 23) Why have you uttered a slander against My children? וקח אתך מזקני ישראל AND TAKE WITH THEE OF THE ELDERS OF ISRAEL as witnesses — that they may see that it is by your agency that the water will come forth from the rock and that people may not say that there had been springs there from time immemorial (Mekhilta). ומטך אשר הכית בו את היאר AND THY STAFF, WHEREWITH THOU SMOTEST THE RIVER — What is the force of the words “wherewith thou smotest the river” — they are apparently superfluous? But these are added because the Israelites had said of the staff that it was intended only for punishment: by it Pharaoh and the Egyptians had been stricken with many plagues in Egypt and at the Red Sea. On this account it is stated here: take the staff wherewith thou smotest the river — they shall see now that it is also intended for good (Mekhilta).

וַיֹּ֨אמֶר יְהֹוָ֜ה אֶל־מֹשֶׁ֗ה עֲבֹר֙ לִפְנֵ֣י הָעָ֔ם וְקַ֥ח אִתְּךָ֖ מִזִּקְנֵ֣י יִשְׂרָאֵ֑ל וּמַטְּךָ֗ אֲשֶׁ֨ר הִכִּ֤יתָ בּוֹ֙ אֶת־הַיְאֹ֔ר קַ֥ח בְּיָדְךָ֖ וְהָלָֽכְתָּ׃

And the Lord said to Moshe, Pass before the people, and take with thee of the elders of Yisra᾽el; and thy rod, with which thou smotest the river, take in thy hand, and go.