This week's Torah portion is called Kedoshim, Saints. Many common and universally accepted concepts in society are expressed in this parashah, such as respect for parents, love of neighbor, the rejection of revenge, and forbidden relationships. Yet, the portion is called "Saints." I mean, people often interpret holiness as something spiritual removed from the material and ordinary. However, according to the Torah, the idea of holiness lies in the fact that even in the most mundane and ordinary matters, a person is different.
The concept of holiness is separation, difference. We call God "The Holy One, blessed be He" because He is removed (at least in revealed form) from everyday life; that is, we do not see Him with our physical eyes, and that is why we call Him Holy.
In this section, God tells us, "Be holy!"—that is, there is a specific command to be holy. Now, it only makes sense to speak of separation and difference where there are two things that are the same. If two things are essentially different, there is no need for a specific command to separate them, because they separate on their own. On the other hand, if two things are essentially the same, it makes sense to speak of differentiation. Therefore, in this section, God commands us to be holy in worldly matters, where all the people of the earth are equal: we all eat, we all sleep, we all wear clothes, and so on. In these matters, we must be holy.
And how does one become holy? By emulating the holy one par excellence, so to speak, God, or, in other words, by following the instructions given by Him on the proper functioning of this universe that He created and, in particular, of this Man that He created, embodied in the Torah.
And where does the capacity to be holy come from? The section continues (Leviticus 19:2), saying, "For I am holy," meaning that the holiness we are commanded to have comes from God's own holiness. If we don't understand it this way, is God simply informing us that He is holy? Then what? Does that mean I must be holy? The verse is explaining why we have the capacity to be holy: because He is holy and shares His holiness with His creatures so that they may emulate Him.