I highly recommend checking out David Guzik's study guide for this week's study on Nehemiah Chapter 12.
http://www.blueletterbible.org/commentaries/comm_view.cfm?AuthorID=2&contentID=7696&commInfo=31&topic=Nehemiah
It is full of great breakdowns of the important concepts, and I love the way he explains the need to purified before we can truly worship God.
Then the priests and Levites purified themselves, and purified the people, the gates, and the wall.
a. Then the priests and Levites purified themselves: They did this first. They could not effectively lead the people in worship of God unless they walked in purity before the Lord.
b. And purified the people: The next did this. They brought cleansing to the people the way the Bible said to, knowing that only a purified people could really worship and praise God.
i. Some might silently object here; they may say, “I know a person who goes to church and seems to be lost in beautiful praise and worship to God, and I also know their life is rather impure outside the church walls. It sure seems they are worshipping God, but are personally impure.”
ii. Something is wrong there; probably, their worship is not a true worship of God in spirit and in truth, but instead a “soulish” experience. All that inwardly moves a person in a deep way is not necessarily of the spirit; it can be of the soul. One of the great works of the Word of God is to divide between that which is truly spiritual and that which is merely soulish (Hebrews 4:12).
iii. Without purity, we can’t worship God in spirit and in truth, as Jesus commanded us to (John 4:24). Psalm 24:3-4asks, Who may ascend into the hill of the Lord? Or who may stand in His holy place? He who has clean hands and a pureheart, and it means it in the sense of bringing praise to God.
iv. We can be made pure and clean before God today, right now, by doing what the Bible says to do - not in following an Old Testament ceremony, but by receiving the word of the New Testament: If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness. (1 John 1:9)