Growing up as a Protestant gave me a different view on what it means to be Holy than I have now, though I believe it still influences me in that respect. My primary example of what I believed was a Holy Man would have to be, and still is in many ways, my grandfather. My grandfather was an old regular Baptist preacher and truly tried to live his life for Christ. He didn't allow many things in his home, from Biology books to “playing cards.” His way of life revolved around Sacred Scripture. He truly tried to set himself apart from the ways of the world.
I think that that in and of itself is a beautiful thing. The word itself, Holy, has roots that point to being set apart, being different. The Old Testament is filled with an example of how that God truly wanted his people to stand out, to be different than those around them. Holiness then rightfully boils down to one statement, though it is not limited to only it in anyway. I will take you as my own people, and you shall have me as your God. (Exodus 6:7) That is how I understand those 613 commandments presented in the Tanakh, as an example of how that the ancient Israelites understood they should behave in that relationship.
The Jubilee years, the Sabbath, the great Jubilee.. all intimate a way for us to do just that. Not only to reflect the extremely personal relationship that they were in with their deity, but also to allow them to do so in a way that reflected who He was. In sharing in His merciful outpouring of grace and forgiveness, they were able to be more like Him. That to me speaks volumes. That God, who did not need rest, allowed us to be able to not only take a rest when we frail humans needed one, but also be able to be more divine in our actions by doing so.
Then the Father took this even further by sending his Son to take on human flesh. By God becoming man he sanctified a way of life. Then speaking in His own words from the sermon on the mount he portrayed to us that propriety in a fullness that expresses what it means to be fully human. God has given us a path through the Beatitudes that exemplifies a paradigm that would change the world if embraced by all people. A paradigm that is best expressed by Jesus himself on the cross. Saint Thomas Aquinas in his eloquent method of speaking expounded on the four spheres of influence that tend to lead to sin. Power, Wealth, Pleasure, and Honor. He surmised that all sin is rooted in one or more of these temptations. Jesus gave us the Beatitudes as a perfect antidote to those spheres, then he lived them out on the cross. As a man on the cross he had no power, he was nailed in place. He had no wealth as they gambled for his clothing on the ground below. He had not pleasure but pain and discomfort. He had no honor but rather the death reserved for the most heinous of all criminals.
In today's society it seems that to be holy is seen as someone who simply attends church regularly, is a 'good' person, and doesn't judge others. To me, being holy has become something even more profound, that is to be more like Christ himself. We should be different, we should be a peculiar and a particular people. Not because we want to be, but because Christ calls us to a radical separation from the world in our manor and behavior. He calls us to Sainthood and a level of perfection that is only possible through releasing control of ourselves to the Holy Spirit. My Grandfather had a powerful idea of how to express that in his conduct and activity, but I disagree with some of his methods. That's truly the crux of the issue. To be holy means to be configured to Christ in our actions and our lives. That might look very different than how the ancient Israelites did it, and in fact it might look different based on our different vocations and stations of life, but it is a calling that every single Christian is called to. It does not mean that we will be perfect or immaculate, but will actualize perfection via a Sacramental life.