Charles Ellicott Commentary Numbers 17:10

"And Jehovah said unto Moses, Put back the rod of Aaron before the testimony, to be kept for a token against the children of rebellion; that thou mayest make an end of their murmurings against me, that they die not." — Numbers 17:10 (ASV)

Bring Aaron’s rod again before the testimony. —Better, Put back (literally, make to return) Aaron’s rod... It is not stated here that the rod was put within the ark. Nor is it so stated in Exodus 16:33 regarding the pot of manna. Neither of these was within the ark when it was brought into Solomon’s temple (1 Kings 8:9); but this statement is by no means inconsistent with that contained in Hebrews 9:4, since the assertion that there was nothing but the tables of the law in the ark at that time does not prove that other things were not in it at an earlier period, and may even suggest that this was indeed the case.

The Jews have a tradition that when King Josiah ordered the ark to be put in the house that King Solomon built, the rod of Aaron, the pot of manna, and the anointing oil were hidden with the ark, and that at that time the rod of Aaron had buds and almonds.