Contradiction with Numbers 8:24
Numbers 8:24 states that the age for Levites to begin service is 25, not 30 as mentioned in Numbers 4:3.
Numbers 8:24: This [is it] that [belongeth] unto the Levites: from twenty and five years old and upward they shall go in to wait upon the service of the tabernacle of the congregation: [to...: Heb. to war the warfare of, etc]
Contradiction with 1 Chronicles 23:24
This verse describes the Levites beginning their service from age 20, which contradicts the age of 30 specified in Numbers 4:3.
1 Chronicles 23:24: These [were] the sons of Levi after the house of their fathers; [even] the chief of the fathers, as they were counted by number of names by their polls, that did the work for the service of the house of the LORD, from the age of twenty years and upward.
Paradox #1
Numbers 4:3 specifies an age range for certain duties, which could be seen as inconsistent with other verses in the Bible that mention different age requirements for similar responsibilities. This might seem like a contradiction in terms of who is considered eligible for certain roles at different times.