Hassidout sur La Genèse 14:13

Or one can say - "Ad-nai appeared to him" (Genesis 18:1) behold, Aner, Eshkol and Mamre were "Avram's allies" (ba'alei brit Avram - Gen. 14:13) even though they were Caananites. [This is why] the text surprises us with "And Ad-nai appeared to him in the woods of Mamre", meaning - how could it be possible for the Holy Exalted Name to appear to him in the woods of Mamre, who was a Canaanite, and doesn't the Holy Blessed One refrain his Shechina from the places of idolaters? And the text said: don't be surprised with this, since " he is sitting at the entrance of the tent", the explanation is that this is the way of the tzadik, even when the tzadik is below, the essence of their sitting is above the Higher Worlds, which are called "tent of meeting", since they [the worlds] are always in joy and happiness as in Yom Tov, and the tzadik is always yearning with their thoughts, and they conquer the going up with their thoughts to the Higher World that is called "sitting at the entrance of the tent". And if you say 'how is it possible that the tzadik is both above and below the higher worlds?' To this the text said: take for yourself the proof in the words "warming up of the day", meaning, from the sun that is above the sky, and the light illuminates downwards, and it looks like as if it is above. So too with the tzadik: they are "as the day is warming up", that they are below, and the light of their Torah and their holiness illuminates above, in the Higher Worlds. And this is "Happy is the man You choose and bring near to dwell in Your courts" (Psalms 65:5), meaning, the Higher World.