The Bible has illustrated different characters and attributes of God. Over and over, Bible authors never failed to proclaim that God is faithful, gracious, slow to anger, compassionate, and full of loyal love. But, among His traits, there is one character of God that needed to be repeated thrice to define the magnitude of this nature – His holiness or Kadosh in Hebrew.
Kadosh, God’s holiness
Today’s definition of ‘holy’ meant being morally perfect or right. Although it may be a part of it, the biblical’s perspective of ‘holy’ is much richer and bigger. It means ‘unique’ or ‘set apart.’
Genesis 2:3 says, “So, God blessed the seventh day and made it ‘kadosh’ because on it God rested from all His work that He had done in creation.” The seventh day is unique among the days and is now set apart for a purpose: to rest from all the work.

So, when the angels declare God as “holy, holy, holy,” they describe Him as Someone incomparable and utterly unique. He is, after all, the Almighty Creator who breathed power into the world, bringing beauty and life.
Encompassing holiness
God’s holiness also affects those around Him. Like when Moses encountered God through the burning bush, God commanded Moses to take off his sandals because the ground he was stepping on has become holy ground.
The same picture goes for the nation of Israel. In the Bible times, God’s holy presence resides in the Temple, located in the center of the community. His holiness affected the entire area that there are specific instructions (found in Leviticus) to maintain purity in the land. Because God’s holiness is too good, man’s impure self cannot stand His holiness, and thus, it will consume us to death (just like Aaron’s sons who violated God’s command).
But, today, Jesus’ holiness has made us able to approach God with confidence. Through Him, we no longer fear death when we come to Him, and we experience the fullness of joy and life with God.
Reference: Youtube | Bible Project