Gemara: The tzitz (plate of gold on the kohen gadol’s forehead) had written on it in two lines: the Name of Hashem on the top and "Sacred for" below [even though it is to be understood as saying "Sacred (kodesh) for Hashem"]. Rabbi Eliezer the son of Rabbi Yossi said: I saw it in Rome, and it has written "Sacred for Hashem" on one line.
Ein Ayah: From a purely philosophical perspective, the source of sanctity must always have precedence over the sanctity itself. Realize that the foundation of sanctity is in being separate from the mundane. This demonstrates to us that the purpose of the mundane is to enable sanctity. This actually brings us to a higher level of understanding, according to which there is, in essence, no difference between sanctity and the mundane because everything reaches its purpose and the highest level does not ignore any element.
In practice, human morality cannot receive the influence it needs from the realization that there is no difference between the mundane and the sacred. [In other words, one needs to be inspired by that which is outwardly seen as sacred.] However, when he calls out with the concept of sanctity [i.e., the word kodesh], and he thereby intends to remove the mundane from the surroundings, he should know that the name of Hashem [which represents all of existence] is above the definition of matters as sacred. It is possible to distinguish between sanctity and its upper side, which receives its special level and value from the loftiness of Hashem, Who is above everything that is great. In that context, it is possible to distinguish and separate between sanctity and the mundane.
The fact that Hashem is above sanctity, which is a very lofty and deep realization, is greater even than the approach one needs to improve his moral level, [which requires him to focus on clearly recognizable sanctity]. This is the way it should be from the perspective of the highest level of philosophical analysis. However, the world is not on the level to appreciate this truth. We are not able to recognize matters that are beyond our level to use to strengthen our moral foundations. If we try, we can damage the moral basis of our spirit. That is why we need to connect all the levels together, even though we then lose the idea that Hashem is above everything, including sanctity. We practically need to lower Hashem to the same line as sanctity, i.e., the holy emotions that a person can feel with his heart. Indeed, it is necessary to lower the truth in favor of peace, for it is the latter that brings a person his moral success. That is why, in practice, "kodesh laHashem" was written on one line.