Jamieson, Fausset and Brown on Hebrews 3:6

6. But Christ--was and is faithful (He 3:2).

as a son over his own house--rather, "over His (God's, He 3:4) house"; and therefore, as the inference from His being one with God, over His own house. So He 10:21, "having an High Priest over the house of God." Christ enters His Father's house as the Master [OVER it], but Moses as a servant [IN it, He 3:2, 5] [Chrysostom]. An ambassador in the absence of the king is very distinguished--in the presence of the king he falls back into the multitude [Bengel].

whose house are we--Paul and his Hebrew readers. One old manuscript, with Vulgate and Lucifer, reads, "which house"; but the weightiest manuscripts support English Version reading.

the rejoicing--rather, "the matter of rejoicing."

of the hope--"of our hope." Since all our good things lie in hopes, we ought so to hold fast our hopes as already to rejoice, as though our hopes were realized [Chrysostom].

firm unto the end--omitted in Lucifer and Ambrose, and in one oldest manuscript, but supported by most oldest manuscripts.