"Woe to the sinful nation, a people whose guilt is great, a brood of evildoers, children given to corruption! They have forsaken the Lord; they have spurned the Holy One of Israel and turned their backs on him." (Isaiah 1:4, NIV)
The people of Israel turned their backs on the Holy One because they wanted to pursue sin. But God, in his holiness, will have nothing to do with sin.
The fact that sin cannot exist in God’s holy presence should inspire us to seek forgiveness when we do something wrong. Our wrongdoing does not put our salvation in jeopardy—Jesus paid for our sins once and for all—but it does affect our closeness to God. If we have unconfessed sin in our lives, we cannot have an intimate relationship with him. We need to confess, ask forgiveness and start fresh. Additional Verses on God's holiness:
“Holy, holy, holy is the Lord Almighty;the whole earth is full of his glory.” (Isaiah 6:3, NIV)
“There is no one holy like the Lord;there is no one besides you;there is no Rock like our God." (1 Samuel 2:2, NIV)
"For it is written: “Be holy, because I am holy.” (1 Peter 1:16, NIV)