Walking with God

The word qadosh (קָדוֹשׁ) in Hebrew or hágios (ἅγιος) in Greek translated as Holy in English means to set apart, to be distinct or unique.

Only God is holy.
Who shall not fear thee, O Lord, and glorify thy name? for thou only art holy: for all nations shall come and worship before thee; for thy judgments are made manifest. (Revelation 15:4 KJV)

Holiness is His most important attribute.
And one cried unto another, and said, Holy, holy, holy, is the LORD of hosts: the whole earth is full of his glory. (Isaiah 6:3 KJV)
And the four beasts had each of them six wings about him; and they were full of eyes within: and they rest not day and night, saying, Holy, holy, holy, Lord God Almighty, which was, and is, and is to come. (Revelation 4:8 KJV)

When a man walk with God who is set apart, he has no choice but to be set apart.
Can two walk together, except they be agreed? (Amos 3:3 KJV)

Walking with God can have wonderful consequences.
And Enoch walked with God: and he was not; for God took him. (Genesis 5:24 KJV)