וַיִּקַּ֥ח מֹשֶׁ֛ה אֶת־הַמַּטֶּ֖ה מִלִּפְנֵ֣י יְהוָ֑ה כַּאֲשֶׁ֖ר צִוָּֽהוּ׃
And Moses took the rod from before the LORD, as He commanded him.
Or HaChaim on Numbers
כאשר צוהו, "as G'd had commanded him." The Torah had to write this in order for us to know that Moses did not delay in carrying out G'd's instructions and took his staff. On the other hand, the Torah may have wanted to emphasise that the only thing Moses did strictly in accordance with G'd's instructions was that he took the staff with him. Anything he did subsequently was not in accordance with G'd's instructions.