Servant chosen to serve the Lord

Numbers 1:44-54
These were the men counted by Moses ad Aaron, total number was 603,550.
The tribe of Levites, however, were not counted along with the others. They are appointed to be in charge of the tabernacle of the Testimony.
The Levites are to be responsible for the care of the Tabernacle of the Testimonyy.
Why?
Levites was chosen to serve the Lord only, they won't go out for fight. The servants of the Lord are be chosen. They have to sacrifice themselves.
The Levites has helped Moses to kill the people who worshiped the golden calf. (Exodus 32:26) So the Levites were chosen to serve the Lord.
How?
Do the right thing the Lord who will remember it. Serve the Lord is an honor but do not have the possession as others. For the servant of the Lord is separate from them and be Holy in present of the Lord.