What does holy, holy, holy mean in reference to God?

from the old testament

• The first of two occurrences of “holy, holy, holy,” is found in Isaiah 6. In this heavenly picture, the Lord is shown to be a majestic king. Above Him are seraphim, angelic like beings who were declaring that the Lord is “holy, holy, holy.” Repeating “holy” three times makes the point that God is entirely holy.
• We see examples of God’s holiness in how God set people and things apart for His glory. For example, in Genesis 2:3 we read, “God blessed the seventh day and made it holy, because on it God rested from all his work that he had done in creation.” God set apart Saturday as a day of rest so that when Jews rested that day, they would remember God’s work in creation.
• In another example, God set aside the Levites as priests to spend their lives serving Him. Speaking about the Tent of Meeting, God said, “There I will meet with the people of Israel, and it shall be sanctified by my glory. I will consecrate the tent of meeting and the altar. Aaron also and his sons I will consecrate to serve me as priests” (Exodus 29:43-44). Notice that God did the “sanctifying” (making holy). To be “consecrated” was God setting the place and priests aside to directly serve Him as only those who are holy can stand before God. So, everything surrounding Him (the tent of meeting, utensils, and people) needed to be made holy. Any unconsecrated thing or person who entered into the consecrated space was instantly destroyed (Leviticus 10:1-3). The “holy, holy, holy” God cannot dwell with sin.
• Even the Levitical priests who had been set aside needed to regularly go through purification rituals to do their duties since being set aside by God did not change their sinful nature. Besides the priests’ regular purification, only the High Priest could enter the holiest place and only once a year (Leviticus 16:2). Before doing so, however, he had to go through a special cleansing to avoid being killed for the short time he was there (Leviticus 16:3-4).
• By setting these boundaries, God was showing His holiness, His uniqueness as the Creator (Genesis 1:1). But, more than that, He is unlike anything in creation because He is completely free from the effects of sin. Old Testament restrictions, therefore, demonstrated His holiness while also protecting the sinful men and women around Him from being destroyed. This separation was visualized by a “veil” that hung between the holy God and sinful people (Exodus 26:33).

from the new testament

• The phrase, “holy, holy, holy” is used in Revelation 4. Like Isaiah, the apostle John was also allowed to peek into heaven. He recorded, “and before the throne there was as it were a sea of glass, like crystal. And around the throne, on each side of the throne, are four living creatures, full of eyes in front and behind: the first living creature like a lion, the second living creature like an ox, the third living creature with the face of a man, and the fourth living creature like an eagle in flight. And the four living creatures, each of them with six wings, are full of eyes all around and within, and day and night they never cease to say, ‘Holy, holy, holy, is the Lord God Almighty, who was and is and is to come!’” (Revelation 4:6b-8).
• In the Old Testament system, the high priest could only enter the consecrated space for a short time to pray for Israel and then had to quickly leave to not be killed. However, “when Christ had offered for all time a single sacrifice for sins, he sat down at the right hand of God” (Hebrews 10:12). The perfect, sinless high priest, Jesus, offered one sacrifice—His own life. He could then remain with the Father, never having to leave.
• When Jesus died, “behold, the curtain of the temple was torn in two, from top to bottom” (Matthew 27:51a). The tearing of the temple curtain (veil) signified that men and women no longer needed to be separated from God. Through Jesus, a way had been made for them to have an eternal relationship with God.
• As the perfect sacrifice, Jesus is the Lamb who is “holy, holy, holy” (c.f., John 1:29) and through whose blood, as we read in Revelation, ransomed (saved) people. Those who are saved do not become perfectly holy in this life (1 John 1:8-10), but they are counted as perfect because the Father looks at what the Lamb did on their behalf (c.f., Romans 4:24-25).
• It is through the Lamb, then, that inherently unholy men and women can dwell with the “holy, holy, holy” God forever (Revelation 21:1-4).

implications for today

Being ‘holy, holy, holy” means that God is entirely distinct from His creation. Not only is He not a created being, but He has also never been tainted by sin. Because He is holy, He cannot allow sinful men and women to be near Him.

While the Old Testament made a way for a few men to work near God’s earthly dwelling place, and one man once a year to come all the way inside, that limited access meant most relied on those few men as go-betweens. Their relationship to God, then, was a highly distanced one.

However, after God sent His Son, access opened up to everyone. However, this does not mean that everyone who is born has a relationship with Him. We are all born sinful and, therefore, God’s enemies. To call Him our Father, we must repent of our sin and trust what Jesus did on the cross. Those who don’t and continue to maintain that they are “good enough,” will not have access to God. Worse than that, those who do not repent and trust in Christ, do not have their sin paid. This means that when they die, the God who is “holy, holy, holy” and cannot be around sin will destroy them eternally for their rebellion.

This is the hard but clear picture of what a holy God demands to be saved from His wrath. Jesus said that He will not cast any one out who comes to Him (John 6:37). If you humble yourself, He and the Father are overjoyed to no longer consider you an enemy, but an adopted son or daughter. When you do this, then the Father will consider Jesus’ holiness as your holiness and your sin as already paid by Jesus.