Exodus 24:4–11 (LEB)
4 And Moses wrote all the words of Yahweh, and he rose early in the
morning, and he built an altar at the base of the mountain and set up
twelve memorial stones for the twelve tribes of Israel.
5 And he sent young men from the ⌊Israelites⌋, and they offered burnt
offerings, and they sacrificed sacrifices as fellowship offerings to
Yahweh using bulls.
6 And Moses took half of the blood, and he put it in bowls, and half
of the blood he sprinkled on the altar.
7 And he took the scroll of the covenant and read it in the hearing of
the people, and they said, “All that Yahweh has spoken we will do, and
we will listen.”
8 And Moses took the blood and sprinkled it on the people, and he
said, “Look, the blood of the covenant that Yahweh has made with you
in accordance with all these words.”
My reading of this is that the sprinkling was symbolic - neither the people nor the tabernacle were actually sprinkled, rather the two representations of the people and the tabernacle mentioned in verse 4 were sprinkled.
The tabernacle and all the utensils did not exist yet - the instructions for building it would be given in the next chapter. Moreover Moses would not sprinkle the blood of the sacrifice on actual flesh as it would defile the flesh.
Rather, there were 12 stones representing the people and there was an altar representing the tabernacle and these were what was sprinkled. Why else would they erect the 12 stones if not to participate in this ceremony? So you have the 12 stones and the altar, and these represented the people and the sacrificial service.
This is why Moses had to say "Look, the blood of the covenant that Yahweh has made with you in accordance with all these words." in order to explain to the people the symbolism of what was happening.
And the author of Hebrews understands this - as would his readers. The reason why I think this must be the authorial intent of Hebrews is because of the panta ("all") in the text:
"he sprinkled all the people"
There wouldn't be enough blood to put even one drop on every individual person and therefore this should not be read literally but symbolically - "all the people" were represented by something that was sprinkled, and Exodus says the twelve stones were what represented the tribes of Israel.
In the same way, the author writes "the tabernacle and all the vessels of the ministry".
Again, there were thousands of vessels - every cup, spoon, hook, stand, plate, pot, lid, etc -- and the tabernacle didn't even exist yet, so something must have represented "all the vessels" -- and this would be the altar.
