Charles Ellicott Commentary 1 Chronicles 23:13

"The sons of Amram: Aaron and Moses; and Aaron was separated, that he should sanctify the most holy things, he and his sons, for ever, to burn incense before Jehovah, to minister unto him, and to bless in his name, for ever." — 1 Chronicles 23:13 (ASV)

And Aaron was separated. — Aaron and his sons, as priests, are thus excluded from present consideration. They form the proper subject of 1 Chronicles 25:1–19, and are only mentioned here for the sake of completeness in the reckoning.

That he should sanctify the most holy-things. — Rather, to hallow (or consecrate) him as most holy; literally, holy of holies (qôdesh qŏdâshîm), an expression not applied to Aaron in any other passage of Scripture. The meaning is that the priests represented a higher grade of holiness, a more thorough consecration, than the mere Levites, because they were called to the discharge of a higher and holier ministry.

He and his sons. — All the priests are included with Aaron.

To burn incense. — The Hebrew term means to burn victims as well as incense.

To minister unto him, and to bless in his name — The same words occur (Deuteronomy 10:8) with reference to the purpose for which the tribe of Levi was separated. The tribe obviously includes the Aaronite clan. (Compare also Deuteronomy 21:5.)

And to bless in his name. — This appears right from Numbers 6:23. Others render, and to bless His name.