Hebrews 4:6

Seeing therefore it remaineth,.... It follows by just consequence, that some must enter therein; for God's swearing concerning some, that they should not enter into his rest, supposes that others should: and they to whom it was first preached; to whom the Gospel was first preached, namely, the Israelites in the wilderness: entered not in because of unbelief; See Heb 3:19.

He specifies this, that we have a promise left us of entering into his rest; that is, of entering into a covenant-relation to Christ, and a state of communion with God through Christ, and of growing up therein, till we are made perfect in glory.

It remaineth that some must enter therein - Why our translators put in the word must here I cannot even conjecture.

God wishes not His rest to be empty, but furnished with guests (Lu 14:23). they to whom it was first preached entered not--literally, "they who first (in the time of Moses) had the Gospel preached to them," namely, in type, see on Heb 4:2. unbelief--Greek, rather "disobedience" (see on Heb 3:18).

Seeing therefore it remaineth that some must enter therein - That is, “Since there is a rest spoken of in the Scriptures, implying that it is to be enjoyed by some, and since they to whom it was first promised did not inherit it, it follows that it must still be in reserve.” This is the conclusion which the apostle draws from the argument in the previous verses, and is connected with Heb 4:9, where he says that “there remaineth a rest to the people of God” - the point to which the whole argument tended. The statement in Heb 4:7, Heb 4:8, is to be regarded as an “interruption” in stating the conclusion, or as the suggestion of a new thought or a new argument bearing on the subject, which he sets down even while stating the conclusion from his argument. It has the appearance of being “suggested” to him as a new thought of importance, and which he preferred to place even in the midst of the summing up of the argument rather than omit it altogether. It denotes a state of mind full of the subject, and where one idea came hastening after another, and which it was deemed important to notice, even though it should seem to be out of place. The “position” in this Heb 4:6 is, that it was a settled or indisputable matter that some would enter into rest. The implied argument to prove this is: (1) That there was a “rest” spoken of which deserved to be called a “divine rest,” or the “rest of God;” (2) It could not be supposed that God would prepare such a rest in vain, for it would follow that if he had suited up a world of rest, he designed that it should be occupied. […]