JOEL - In preparing the 1835 D&C edition, Joseph Smith and a committee appointed to the task on September 24, 1834 (HC 2:165, 243-44) edited the revelations that had formerly appeared in the Book of Commandments. They corrected scribal and printing errors and occasionally clarified the text. They also combined some of the revelations to simplify publication and corrected grammatical problems.
One of these clarifications appears in the 7th chapter of the Book of Commandments which, refering to Oliver Cowdery, states:

"Now this is not all, for you have another gift, which is the gift of working with the rod: behold it has told you things: behold there is no other power save God, that can cause this rod of nature, to work in your hands, for it is the work of God; and therefore whatsoever you shall ask me to tell you by that means, that will I grant unto you, that you shall know." (BOC 7:3)

This is how it now reads in D&C Section 8:
8:6 Now this is not all thy gift; for you have another gift, which is the gift of Aaron; behold, it has told you many things;
8:7 Behold, there is no other power, save the power of God, that can cause this gift of Aaron to be with you.
8:8 Therefore, doubt not, for it is the gift of God; and you shall hold it in your hands, and do marvelous works; and no power shall be able to take it away out of your hands, for it is the work of God.
8:9 And, therefore, whatsoever you shall ask me to tell you by that means, that will I grant unto you, and you shall have knowledge concerning it. (D&C 8:6-9)

The phrases "gift of Aaron" and the "gift of working with the rod"(BOC 7:3), both refer to the gift Aaron had of being able to use the power of God through the rod he carried to help Moses perform his miracles:

"And they did so; for Aaron stretched out his hand with his rod, and smote the dust of the earth, and it became lice in man, and in beast;" (See Ex 8:16-17, Num. 17: 6, 8).

Oliver Cowdery was given a similar rod or gift, a gift of revelation, which he used to help Joseph Smith translate the Book of Mormon(D&C 8:11, 28:3). In the D&C the name of this gift was changed to read the "gift of Aaron"(D&C 8:6-9), perhaps to emphasize the similarity between Oliver's and Aaron's gifts, which they used to help their respective prophets perform God's work.
The Book of Mormon also seems to associate the use of a rod with the work of Joseph Smith:

"And the Lord hath said: I will raise up a Moses(Joseph Smith); and I will give power unto him in a rod; and I will give judgment unto him in writing." (2 Ne 3:17)

There are indications that Oliver may have actually possesed a rod or staff, similar to Aaron's, which may have served as a symbol of this "gift of Aaron", which he used like a seer stone, to reveal truths from God; something he could hold in his hand as indicated in D&C 8:8. A notation in Anthon H. Lund's Journal for July 5,1901 states:

"in the revelation to Oliver Cowdery in May 1829, Bro. [B. H.] Roberts said that the gift which the Lord says he has in his hand meant a stick which was like Aaron's Rod. It is said Bro. Phineas Young [brother-in-law of Oliver Cowdery and brother of Brigham Young] got it from him [Cowdery] and gave it to President Young who had it with him when he arrived in this [Salt Lake] valley and that it was with that stick that he pointed out where the Temple should be built."

Critics of the church like to imply that the "gift of working with the rod" refers to a typical y-shaped divining rod that Oliver Cowdery used in the superstitious practice of divining for water. Although divining for water was a common practice in those days, other historical records have described the rod, more like that of Aaron's, as a long staff that was held in one hand. If Aaron could have one, why not Oliver?