Matthew Poole and continuators on Hebrews 9:8

8 The Holy Ghost this signifying, that the way into the holiest of all was not yet made manifest, while as the first tabernacle was yet standing .

God the Spirit himself, the third Relation in the Deity, the Author of all the Mosaical Institutions, who commanded all these ritual Ceremonial Services in this Tabernacle to be performed, who revealed all this to Moses, and who inspired him with it, Levit. 16.1, 2. The most infallible Interpreter of his own Institutions, declared by these Signals and Types, and demonstrated by the frame of Ordinances, then given to the Church in these expressions, Exod. 30.10. Levit. 16.2, 12, 13, 14, 15, 17. The Veil ever covering the Holy of Holiest, but only in the day of Expiation, when it was drawn aside and that laid open.

The true and very means to God's Presence in Heaven it self, which is only by Christ the great High-Priest, through whose Blood we can come to the Throne of his Grace there boldly, chap. 10.19, 20, 21, 22. and by the perfect work of his Spirit on us, can enter with him into the Holy of Holiest in Heaven. This was not so plainly, clearly, fully, universally known as afterwards by the shedding of Christ's Blood, and the Revelation of it in the Gospel to all the World. Christ was revealed to the Hebrews, and all these Ceremonial Ordinances did hold him out, and by him only, the Saints under that Covenant-Administration got to Heaven, yet the manifestation of it was obscure in comparison of what it is since.

While the Mosaical Covenant-Administration was to concontinue, till the coming of Christ in the Flesh, and perfecting the work by his Death, for the space of near 1500 years was the true, right, and proper way for entring into Heaven, darkly, and obscurely, and typically revealed unto the Church, when by the Death of Christ the Vail of the Holy of Holiest was rent asunder, Heaven laid open to be seen, and entred into by all penitent believing Sinners through Christ, every day in their Duties, and then in their Persons; Matth. 27.51.

Marginal references: John 14.6.