A death certificate indicates that a relative was born Rush County, Indiana, on 23 December 1846.
The tombstone indicates that the relative was born on 25 December 1846.
The 1850 census indicates that the same relative was a native of Indiana and was three years of old at the time of the enumeration. That means that the person was born in either sometime in 1846 or 1847. It’s not additional evidence that the person was born specifically on 23 December 1846. It is consistent with that date of birth (which is good), but the census does not indicate that precise date of birth.
Use the death certificate as the source for the 23 December 1846 birth in Indiana.
Use the tombstone as the source for the 25 December 1846 birth. Don’t use the tombstone for as a source of the Indiana place of birth since the stone does not provide a place of birth.
Use the census as the source for a 1846-1847 birth in Indiana.
Choose which date you believe to be more reliable and make that your “preferred” date of birth for the person in question. In your notes indicate why you believe that date/place to be the most accurate.
Avoid indicating sources say things that they do not. It will reduce confusion later–especially if other records disagree.