Albert Barnes Commentary 2 Samuel 5:3

"So all the elders of Israel came to the king to Hebron; and king David made a covenant with them in Hebron before Jehovah: and they anointed David king over Israel." — 2 Samuel 5:3 (ASV)

Before the Lord - Abiathar and Zadok the priests were both with David, and the tabernacle and altar may have been at Hebron, though the ark was at Kirjath-jearim.