The families of the oldest brother were treated the same as those of the youngest

1 Chronicles 24:1-31
The Divisions of Priests
These were the divisions of the descendants of Aaron: The sons of Aaron were Nadab, Abihu, Eleazar, and Ithamar. But Nadab and Abihu died before their father did, and they had no sons; so Eleazar and Ithamar served as the priests.
A larger number of leaders were found among Eleazar’s descendants than among Ithamar’s, and they were divided accordingly: sixteen heads of families from Eleazar’s descendants and eight heads of families from Ithamar’s descendants. They divided them impartially by casting lots.
Total is 24 orders. This was their appointed order of ministering when they entered the temple of the Lord, according to the regulations prescribed for them by their ancestor Aaron, as the Lord, the God of Israel, had commanded him.
The rest of the Levites.
These were the Levites, according to their families. They also cast lots, just as their relatives the descendants of Aaron did, in the presence of King David and of Zadok, Ahimelek, and the heads of families of the priests and of the Levites. The families of the oldest brother were treated the same as those of the youngest.
Twenty-four groups of priests - all tracing their family lines back to Moses's brother Aaron, the first high priest - were to be in charge of the Temple sacrifices, each serving for two weeks a year. The order was decided by lot.
Why?
To be a priest in the order is the honor in Levites. Both are the descendant of Aaron.
Make an order and serving jobs are decided by lot. It is righteousness and just to everyone.
God is the Lord and David knew the mind of the Lord so he makes these orders to serve the Lord in the Temple.
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依祭司分24個,班次，這首領食抽籤來決定，有組織、有秩序的。不是隨性的。有工作的時候，有休息的時候。不是特別累，特別少的。教會中有人能力強，就包了許多事來做，別人沒有機會做。外加除了在聖殿工作外，還要在百姓當中做教導的工作。
利未人也分班次，
祭司用神的話教導，也以身作則，在生活中成為百姓信仰的帶領者。，成為眾人的榜樣。
宣揚神的美德，不是只有嘴裏說，而是行出來。
班次不能選，不能換選，這兩週要分別出來。服事是要分別出來，那個時間是為了服事神。
只要弟兄姊妹有預備，讓大家有機會服事人
 不能單獨完全單獨個人來做。很熱心外，也要彼此分擔。 
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How?
Our heart is more important than any other like the church is a building, but the Christian in the church is more important.