For I am the LORD who brought you up out of the land of Egypt to be your God. You shall therefore be holy, for I am holy.”. This would not be problematic if it was not for 1 Peter 1:16 which quotes it. So at least one biblical writer thought it applied to Christians as well as Jews. But what does "Holy" mean. Initially it seems in context to have done with ritual purity but then Christians have a different understanding of what makes a person unclean see Matthew 15:11 and refers it to moral deeds done by a person. However I am going to suggest that we learn more about what being Holy entails if we see it as reflecting God. So what are the characteristics that seem to specifically define God as worshipped by Christians. I would suggest that chief amongst them is generous, faithful love.
Generous - In some ways we need to come to terms with this. God's love is never sensible in its generosity. God does not seem to give us what we think as practical or even what we think we would like. God is frustratingly the sort of person who decides we need a diamond ring when what we were looking for was a good night out. God is capricious and overwhelming. There is not saying what he will do, but you equally can't be sure that he won't permit or do something. I don't know why, but I do know that if God's action on the cross is what Christians claim it is, then no amount of prayer not answered can balance the books. The problem is that God is does not seem to keep account and give fairly. Generosity in this sense is not about amount its about openness. So our response needs to have some of the lack of calculation that God's response to us does.
Faithful - There is as saying that goes "When the going gets tough, the tough get going" and that really is the core of being faithful. God has a habit of turning up in the darkest of places. He rescues Israel from Egypt not in Joseph's day, but when they were basically slave labour. He does not decide to come in person when things in Israel are going well and turns up at the palace, he comes when Israel is occupied and gets himself killed by the occupying authorities. Now lets be clear I don't trust God for one moment to get me out of trouble, he may, he may not; I do trust God to be there in times of trouble.
Love - forget romantic attraction, this seems to be more positive regard. Well wishing that is followed through into practical action.If you prefer unconditional regard for all of creation and all creatures with it. Another is that God enjoys creation, much as many men enjoy hobbies, the are serious about it, often quite nerdishly so and gain satisfaction from doing it. God does not need creation but it flows out of the very nature of God. That is important, God's love comes first. The challenge for the Christian is to mirror this sort of connection back at God and onto creation. As we do it towards creation we become co-creators with God, as we do it to God we honour and enjoy him.