Levites they are not to come near to serve me as priests

Ezekiel 44:1-14
The price himself is the only one who may sit inside the gateway to eat in the presence of the Lord.
The Levites who went far from me when Israel went astray and who wandered from me after their idols must bear the consequences of their sin. They may serve in my sanctuary, having charge of the gates of the temple and serving in it; they may slaughter the burnt offering and sacrifices for the people and stand before the people and serve them. But they served in the presence of their idols ... they are not to come near to serve me as priests or come near any of my holy things of my most holy offerings.
Everything is perfect, This is the ideal. Yet it is not as far-reaching as the vision in Revelation. It is still a Temple and sacrifices: the people of God are synonymous(代名詞) with Israel.
By the prince here is probably meant the chief governor of the Jews after the captivity, such as were Zerubbabel and Nehemiah, for Sheshbazzar, or Zerubbabel, is called the prince of Judah
This chapter contains ordinances relative to the true priests. The prince evidently means Christ, and the words in ver. 2, may remind us that no other can enter heaven, the true sanctuary, as Christ did; namely, by virtue of his own excellency, and his personal holiness, righteousness, and strength. 
Why?
New regulation of the Temple, Levites can server people, but they can not serve the Lord and near the Holy matter for their sins.
God wants his servant be holy and honest to serve Him/
How?
Serve the Lord with Holy heart and Holy behavior. For God is holy.