“who kept my instruction.” The section for the priests is for priests who were faithful to God during their lives and did not abandon the Law and go astray after idols and participate in other such sins. There has always been a difference between salvation and rewards. Salvation is, and always has been, by grace through trust in God. In contrast, rewards are earned for serving God and will be given out during the Millennial Kingdom of Christ. In this case, part of the rewards for faithful priests is that they get to live in the priestly area that contains the Temple. God does not tell us where priests who got saved but were unfaithful get to live in the Millennial Kingdom.
[For more on rewards in the Kingdom, see commentary on 2 Cor. 5:10, “good or evil.” For more on the Millennial Kingdom on earth, see Appendix 3, “Christ’s Future Kingdom on Earth.”]