Hebrews 10:16
Hebrews 10:1616“This is the covenant I will make with them after those days, declares the Lord. I will put My laws in their hearts and inscribe them on their minds.”
quotes — "I will put my laws in their hearts, and in their minds I will write them." The Watchtower reads this as a promise to the 144,000 "spiritual Israel" who are the parties of the new covenant, not to the great crowd. The indwelling-Spirit aspect — laws written on the heart — is assigned to the anointed; the great crowd receives instruction through the organisation rather than directly.
The verse itself is the citation the entire new- covenant argument rests on, and the verse immediately following (, quoting ) adds: "their sins and their lawless deeds I will remember no longer." The covenant's central benefit is forgiveness of sins — and the Jeremiah promise explicitly reaches "from the least of them to the greatest" (; ). If "the least" is excluded, the "from-the-least-to-the-greatest" language means nothing. Every believer is a party to the new covenant, because every believer needs the forgiveness the covenant secures. Pair with ("drink from it, all of you, for this is my blood of the covenant... for forgiveness of sins") — Jesus did not restrict the cup to a subset, and the covenant's stated purpose is forgiveness of sins, a universal human need.