Leviticus 21  - Adonai gave specific instructions for the priests.  They were held to a higher standard because of the greater importance of their responsibilities.  They were "set apart as holy".   These instructions included how they lived, who they married, how they cut their hair and beards,  and whose funerals they could attend.  Everything was governed by the fact that God made them holy.

Leviticus 22 continued this emphasis on holiness, teaching that even the things they touched were subject to whether the thing was holy or unclean.  There are also instructions here about the nature of the sacrifices, especially that they were perfect and acceptable.. " I am to be regarded as holy among the people of Israel; I am Adonai, who makes you holy....." 

Leviticus 23 includes the instructions for the Sabbath and the Holy feasts and ceremonies that Israel would observe.  These days are God's "designated times" according to the Complete Jewish Bible.
There was the celebration of Firstfruits,- a spring celebration of the barley harvest;
 Pentecost- 50 days later would celebrate the first-fruits of the wheat harvest.
 Rosh-Hashanah was set apart for remembering and regathering, a day for repentance and self-evaluation;  leading up to -
Yom Kippur - The day set aside for atonement- the most holy day.

When the temple was destroyed in 70 AD, there was a change in how the people of Israel could observe these designated times of Adonai.  Yet, there is still a yearning and hope for the rebuilding of the Temple one day. Holy vessels and priest's garments have been prepared. That day will come. Maybe soon.

Father in heaven, we give thanks to You for all that You provide.  You give the rain and sunshine that food may grow and be harvested.  You give to us daily bread and we thank You.  Thank You for the Living Bread,  for Jesus Christ who is the One who makes us holy as He lives in us who believe in Him. Teach us to take time to remember, to regather, to repent, and to find renewal in You day by day. We long for the day when we will see You face to face and truly understand what holiness really means.  Thank you for the truth of Your Word that teaches us so much about who You are.  We give all praise and honor to You.  In Jesus' name. amen.