Kabbalah su Isaia 38:2

Rabbi Shimon opened the discussion by speaking about the verse: "Then Hezekiah turned his face to the wall, and prayed to Hashem" (Isaiah 38:2). Come and see how powerful is the might of the Torah, and how high it rises above all! Because whoever conducts his life according to the Torah has no fear of those above or below, and mishaps or illnesses of this world do not concern him. Through the Torah, he is attached to the Tree of Life and learns from it every day.

The friends said that when a man prays nothing may come between him and the wall, as it is written, "Then Chizkiyahu turned his face toward the wall" (Isaiah 38:2). When a man prays, no one may come within four cubits of him on every side. They said this means four cubits on every side except in front. And they said that a man should not pray behind his Rabbi. They appointed me about these matters.