John Calvin Commentary Hebrews 9:5

"and above it cherubim of glory overshadowing the mercy-seat; of which things we cannot now speak severally." — Hebrews 9:5 (ASV)

Of which we cannot now, etc. Since nothing can satisfy overly inquisitive people, the apostle cuts off every occasion for elaborations unsuitable for his present purpose, so that a longer discussion of these things does not break the thread of his argument. If, therefore, anyone should disregard the Apostle’s example and dwell on the subject in greater detail, he would be acting very unreasonably.

There might, indeed, be an opportunity to do this elsewhere; but it is now better to focus on the subject he is addressing: it may further be said that to philosophize beyond proper limits, which some do, is not only useless but also dangerous. There are some things which are clear and suitable for building up faith; however, discretion and sobriety should be observed, so that we do not seek to be wise beyond what God has been pleased to reveal.