The priests came from their various homes to be a part of this celebration. Yes, there was much singing and gladness and thanksgiving — but this was not done lightly. During this celebration, even before the choirs were convened and the march around the city commenced, we see that the priests had to purify themselves first, then the people, and then the gates of the wall.
Hebrews 9:11-14 puts it in the context of us as New Testament people. We need a Lamb even now
But when Christ appeared as a high priest of the good things that have come, then through the greater and more perfect tent ( not made with hands, that is, not of this creation)  he entered once for all into the holy places, not by means of the blood of goats and calves but by means of his own blood, thus securing an eternal redemption.  For if the sprinkling of defiled persons with the blood of goats and bulls and with the ashes of a heifer sanctifies for the purification of the flesh,  how much more will the blood of Christ, who through the eternal Spirit offered himself without blemish to God, purify our conscience from dead works to serve the living God.
If we desire to worship our Lord Jesus Christ, along with that is a desire for purity before him. Does not Jesus say in his Sermon on the Mount say, “Blessed are the pure in heart, for they shall see God” (Matthew 5:8). The priests understood the law that God had given to Moses: you cannot truly worship and truly present yourself before me unless you have a desire for purity. If you want to truly “see God” and know him in all his fullness, pursue him with a desire for purity.
Proverbs 22:11 says:
He who loves purity of heart,
and whose speech is gracious, will have the king as his friend.
Does this also apply to Jesus as well? What about you this morning? Are you here pursuing purity? Are you here to know God? Are you here to be gripped by his gospel? Are you here desiring to obey? If there is impurity in your heart, then it must be dealt with. Remember Jesus’ words in Matthew 5:23-26:
So if you are offering your gift at the altar and there remember that your brother has something against you, leave your gift there before the altar and go. First be reconciled to your brother, and then come and offer your gift.  Come to terms quickly with your accuser while you are going with him to court, lest your accuser hand you over to the judge, and the judge to the guard, and you be put in prison.  Truly, I say to you, you will never get out until you have paid the last penny (Matthew 5:23-26).