[These are people] who were once enlightened [by the Gospel message], who had experienced the gift from heaven [i.e., forgiveness, never ending life, etc. See Rom. 6:23], who had partaken of the Holy Spirit [See Acts 2:38],

Now after preparing these things [i.e., the table, incense, etc.], the priests regularly enter the outer room of the Tabernacle [i.e., the Holy Place] to carry out the duties of their service.

Therefore, it was necessary for the copies of the heavenly things [i.e., the Tabernacle, its furniture and utensils, etc.] to be [ceremonially] cleansed by these things [i.e., the blood of animal sacrifices], but the heavenly things themselves [i.e., the church, both on earth and in heaven] require better sacrifices than these [i.e., the sacrifice of Christ].

Now the words, "once more" indicate the removing of what can be shaken --- that is, the created universe --- so that those things which cannot be shaken will remain. [Note: These "things" have been variously interpreted to be eternal truth, the heavenly kingdom, the new heavens and earth, etc.].