“וַיִּשָּׂא עֵינָיו, וַיַּרְא, וְהִנֵּה שְׁלֹשָׁה אֲנָשִׁים, נִצָּבִים עָלָיו; וַיַּרְא, וַיָּרָץ לִקְרָאתָם מִפֶּתַח הָאֹהֶל, וַיִּשְׁתַּחוּ, אָרְצָה”
“He lifted up his eyes and looked, and behold, three men were standing in front of him. When he saw them, he ran from the tent door to meet them and bowed himself to the earth”
When Abraham saw the three angels, he also saw the Shechina with them and he bowed down. Jacob also bowed in front of the Shechina
In Genesis 47:31 we also read about Jacob bowing toward the head of his bed because he saw the Shechina.
“וַיֹּאמֶר, הִשָּׁבְעָה לִי–וַיִּשָּׁבַע, לוֹ; וַיִּשְׁתַּחוּ יִשְׂרָאֵל, עַל-רֹאשׁ הַמִּטָּה”
“He said, “Swear to me.” So he swore to him. Then Israel bowed in worship at the head of the bed.”
Jacob was ready to leave the world and called his son Joseph with instruction related to his passing. The sages teach us that the Shechina visits the sick at the head of their bed.
We may not be able to see the Shechina but we still bow down in her presence several times during the silent prayer (more here: Amida), when we bless with the YHVH name, saying “Baruch Ata YHVH…”. Regular blessings do not require bowing, only the ones that put us on higher level. The silent prayer is in the world of Atziluth and our prayers is in front of the Shechina. When a person goes up (Aliyah) to the Torah, he bless and bow because next to the Torah on Shabbat he is in an ‘elevated’ state.
When we bow down we lower ourselves to Malchut and when we rise up we connect to the shechina in front of us. We go down in ‘Baruch’, bow down in ‘Ata’ and rise up with the YHVH name.
“וַיֹּאמַר: אֲדֹנָי, אִם-נָא מָצָאתִי חֵן בְּעֵינֶיךָ–אַל-נָא תַעֲבֹר, מֵעַל עַבְדֶּךָ.”
“and said, “My lord (ADNY אֲדֹנָי), if now I have found favor in your sight, please do not pass your servant by.”
Abraham refers to the Shechina with the name אדני ADNY. We use this name to read the YHVH name. The light of YHVH is revealed in Malchut with the name ADNY אדני. The literal meaning of this name is ‘master’ because as a master of the world, the Shechina connects Yessod and the three worlds above to Malchut.
This verse is in singular form to teach us that Abraham saw the Angels with the Shechina as one because they represented Zeir Anpin, which is a male aspect. Z”A delivers light through Yessod to Malchut. In the verse that follows (Genesis 18:4), Abraham refers to them in plural form when offering the angels water and food.
We learn here that the Shechina draws the light from the supreme source above, which is Binah that delivers the upper lights to the three columns.