Vayera - to fear, to stand in awe, to respect
Abimelech said to Avraham regarding his disrespect for Sarah (by putting her honor in danger by calling her his sister and disclaiming her as his wife) - "you have done deeds that ought not be done." Bereshit 20:9
מַעֲשִׂים אֲשֶׁר לֹא-יֵעָשׂוּ, עָשִׂיתָ עִמָּדִי
Did Avraham learn? Elohim comes to test.
In the next chapter (Bereshit 21:14), Avraham has disrespect for Hagar, by putting her life in danger. In fact, Avraham's "deeds that ought not be done" have escalated from endangering a woman's honor to endangering a woman's life (and additionally, the life of her son). Avraham has not learned respect.
Elohim comes to test again Avraham's respect for the lives entrusted to his care and asks Avraham to take Isaac's life by his own hand (Bereshit 22:2). Avraham hurries to comply. Avraham still has not learned, and this is the third time Avraham has been tested in this area. If the Divine had allowed Isaac to be sacrificed by Avraham, his disrespect for the lives and welfare of those in his household would have become a solid chazakah according to Jewish law and a permanent characteristic of Avraham.
Hospitality to angels means nothing if one fails to care for those in his or her own household.
The dynamics of a negative chazakah and the true merit of Avraham:
First time, Avraham has no concern at all for Sarah and is not aware that his action is wrong until Abimelech creates the awareness in him. Abimelech brings to the surface a conscience in Avraham. Now choice exists in Avraham between selfishness and selflessness, between strengthening the power of ulterior ego motivation or strengthening the ego's rectified power of chen.
Second time, Avraham is now aware that what he is about to do to Hagar and her son is wrong, yet he does it anyway despite that the deed felt "very grievous" to him. Avraham ignores his conscience.
Third time, having silenced the natural revulsion that he now has toward 'doing the wrong deed', Avraham hurries to do it. Avraham is killing his conscience and reverting to barbarism. The Divine steps in, preventing Avraham's complete reversion for the sake of humankind on account of the Divine oath given to Noah that there shall never again be a flood to destroy the earth with reversed chesed v'chen.
The Divine Oath inspired (chinuch) by Noah found a point in Avraham oriented toward integration (hadracha) into human consciousness despite his wrong deeds. This is Avraham's true merit.
Follow-Up: The Flaw Of Pure Selflessness