Chazal say "גדולה הכנסת אורחים יותר מהקבלת פני השכינה" - Greater is hosting guests than receiving the face of the שכינה. This is derived from the fact that Avraham Avinu interrupted the visit from Above in order to receive guests.
This means that he was willing to forgo his own growth in order to give to others. He could have reached SUCH HIGH MEDREIGOS by continuing to be in the presence of the שכינה. But instead he decided to attend to the needs of three strangers.
Moshe Rabbeinu similarly told Hashem after the cheyt ha-eigel: Either bear their sin or "מחני נא מספרך אשר כתבת" - erase me from Your Book. This was a classic example of mesirus nefesh for the larger community. He was willing to lose his own levels and be erased from the eternal Torah on behalf of the Jewish people.
That is the middah of Avraham Avinu: His chesed EXTENDED to others - התפשטות החסד! He nullifies himself and his own wants and needs in order to bring benefit to others.
Yitzchak was the opposite: He was gevurah!! He focused on the central point of his soul and didn't allow it to spread in order that it should be completely concentrated on Hashem and His will and be revealed in all of its glory. The contraction of the self. "Akeidas Yitzchak" - The BINDING of Yitzchak. THAT is his middah.
That is why the Beis Hamikdash is built on the place of Akeidas Yitzchak which represents the combination of the two pillars - chesed and gevurah [as the Sifri says]. In other words the Beis Hamikdash is comprised of concentrated kedusha in its very place together with the expansion of Kedusha to the whole cosmos. This is the incorporation of the middos of Avraham and Yitzchak in the place of the Beis Hamikdash.
The middle of the road is the middah of Yaakov - Tiferes, that on one hand the kedusha is concentrated in the Torah [Tiferes is Matan Torah - see Brachos 58a]. On the other hand, the influence of the Torah expands to all of creation because the blueprint for the world was Torah and anyone can come and take it.
[עפ"י הס' ואני תפילה עמ' כ"ח]
