John Gill Commentary 1 Chronicles 9:19

"And Shallum the son of Kore, the son of Ebiasaph, the son of Korah, and his brethren, of his father`s house, the Korahites, were over the work of the service, keepers of the thresholds of the tent: and their fathers had been over the camp of Jehovah, keepers of the entry." — 1 Chronicles 9:19 (ASV)

And Shallum the son of Kore
The same as in (1 Chronicles 9:17) whose pedigree is traced up to Ebiasaph the son of Korah, see (Exodus 6:24)

and his brethren, of the house of his father, the Korahites ;
so called, because they descended from Korah:

[were over] the work of the service, keepers of the gates of the
tabernacle ;
until the temple was built:

and their fathers being over the host of the Lord ;
the Levites, who were the Lord's army, and whose service is represented as a warfare, (Numbers 4:5)

[were] keepers of the entry ;
into the tabernacle, that none might enter that were impure; or into the court of the priests, excepting priests; or into the holiest of all, as Kimchi suggests.