Charles Ellicott Commentary 2 Chronicles 1:6

"And Solomon went up thither to the brazen altar before Jehovah, which was at the tent of meeting, and offered a thousand burnt-offerings upon it." — 2 Chronicles 1:6 (ASV)

And Solomon went up there to the brasen altar. —So the Vulgate incorrectly. Rather, And Solomon offered there on the brasen altar; so the Septuagint and Syriac.

Before the Lord. —The altar stood before the entry of the Lord’s dwelling place (Exodus 40:6). (Judges 20:26.)

Which was at the tabernacle of the congregation. — Which altar belonged to the tent of tryst. In 1 Kings 6:22 the golden altar is said similarly to belong to the Holy of Holies, before which it stood. (The Vulgate seems to have read “the brasen altar, before the Lord’s tent of meeting”; compare 2 Chronicles 1:3.)

And offered. — He offered (I say). The verb is repeated before its object for clarity's sake.