I suppose I was not clear in my writing, Kosonen.😊 I did not distinguish between "A new covenant" and "The new covenant."
The covenant spoken of at Jeremiah is talking about all Christians being God's kids, having God's law in their hearts.
The covenant Jesus instituted involving the emblems was made specific with certain Christians who will be part of the 144,000 and sit on thrones and do a specific assignment. That's why Revelation says they come out of that group, they are a representative sample of that group.
"and I make a covenant with you, just as my Father has made a covenant with me, for a kingdom, so that you may eat and drink at my table in my Kingdom, and sit on thrones to judge the 12 tribes of Israel."
"Jesus said to them: “Truly I say to you, in the re-creation, when the Son of man sits down on his glorious throne, you who have followed me will sit on 12 thrones, judging the 12 tribes of Israel."
The Levites of old were taken for an assignment as a representative sample of the nation. It wasn't because they were smarter or more special or whatever. The priests wore an ephod, an apron, because they were working in a slaves position for their brothers, to minister to them for a purpose.
Hebrews 8 and 9 has many references back to Leviticus. Not all the Israelites took part in the sacrifices at the tabernacle. The book of Leviticus could be read or heard by all Israelites, but only the priests and Levites were required to handle the certain duties written about in that book. Even when King Uzziah later tried to usurp the place of a priest, Jehovah did not look positively on that action.
All Israel were brought into the covenant with Jehovah, and all Christians are in a new covenant with Jehovah by means of the Christ's blood. But the specific duties of the 144,000 priest/kings are different. Not all Christians need to partake. It's not necessary. Faith and love are necessary. Only those who need to be a new creation in order to go to heaven, since flesh and blood cannot enter heaven, only those who need to work in the figurative temple need to give up their physical bodies and be given spirit bodies. Christians who will be living on earth don't need a spirit body.
All Christians will get to see God when He comes here. All Christians will get to hang out with God and Christ, because they can come to earth. There is no need to covet the assignment of another or to encourage people to eat what belongs to the priests. There is enough love and food for everyone.