In the Old Covenant, God only authorized men from the tribe of Levi to be in charge of the operation of worship and sacrifice in the Tabernacle and Temple (Numbers 1:47-54). They were called His priests. Anyone not of the tribe of Levi would die if they touched the articles of the Tabernacle and Temple, because they were holy, or offered sacrifices. Of the priests in the tribe of Levi, only the descendants of Aaron were authorized to serve as High Priest. The High Priest's job was to actually enter and sacrifice in the Holy of Holies once a year. Again, death was the result of failing to observe this command. The tribe of Levi was the chosen tribe set apart for this special purpose to facilitate access to the presence of God and His worship.
The New Covenant, amazingly, tells us that all believers in Jesus Christ are actually the New Covenant priests whether men, woman or children (2 Peter 2:4-10). Because of the sacrifice of Jesus on the Cross, the Spirit now dwells in our hearts and we all have access to the presence of God without a human priest. In fact, Jesus is the New Covenant High Priest forever and not of the line of Aaron, which ended with the destruction of the Old Covenant Temple, but of the greater and more perfect order of Melchizedek (Hebrews 7:11-19 9:6-15).
Now that all believers are New Covenant Priests with full access to God, He provides His people with certain men who are called to facilitate the worship and oversight of His Church: elders and deacons (I Timothy 3:1-13). Instead of needing servants like the Levites to protect the people from His presence, in the New Covenant God calls elders and deacons to tend the growth of His people. It is through the ministry of the elders and deacons that God leads His church into ever increasing faithfulness, maturity, and oneness with Him.