Each of the seven days of Sukkot is associated with a Biblical figure. They are nicknamed the “ushpizin” as they are considered ‘guests’ that you invite into your sukkah. This is symbolic of focusing on a specific attribute of that person. These attributes correspond to the seven middot, the lower seven emanations (Sefirot) of G-d that are ‘active’ in creation. As we focus on a particular attribute we examine aspects of it at all levels – physical, emotional, intellectual and spiritual.
Abraham is the first of the ushpizin (guests) we welcome during Sukkot. Chesed (‘lovingkindness’ or ‘mercy’) is associated with Abraham. Chesed is the active, giving, aspect of God. Abraham was known for not waiting to be kind to others. Chesed is not only first in terms of hierarchy, but also in that it has nothin g ‘causing it.’
‘The world is built with chesed.’ (Psalm 89:3)
Even before his reputation for hospitality became known, Abraham was the model of being proactive. He searched for and discovered G-d on his own, while rejecting the idolatry of his contemporaries.
Abraham did not allow his environment to dictate his choices. He carried out G-d’s commands with eagerness and speed, such as when G-d told him to:
1. travel from his homeland to Canaan.
2. circumcise himself
3. offer his son Isaac to G-d. (i.e., He “rose early in the morning,”)
‘The scrupulous do the Mitzvoth immediately.’ (Yoma 28b).
Conversely, just as chesed has no borders, Abraham lacked the ability to distinguish between Isaac and Ishmael. G-d sent Sarah as his ‘personal’ counterbalance. The ability to make distinctions comes with the second of the middot – Gevurah/Judgment.
http://www.13petals.org/topical-studies/ushpizin-movie-web/ushpizin-themes/ushpizin/