God is Holy, which means that he is separate, He is set apart from all else that is. This otherness is an essential part of his nature. When God’s people and God’s angels cry out that he is “holy, holy, holy” they are confessing with force that God is holy in his essence, in all that he is and does, and that this attribute is central to what makes God, God. Tied into this his holiness means that he is absolutely pure, completely unstained by sin or evil. As Christians this is essential to know because in his holiness he calls those of us who are his people, his children to reflect him by also being holy. We are to be holy first and foremost because our God and our Father is holy and he alone is the standard by which holiness is to be measured or judged.