The Akeidah as a test in yirah

בנסיון העקידה כתיב וירא מרחוק כו' כי הקב"ה ניסה אותו במדת היראה כי עיקר מדתו הי' אהבה וקירבות כמ"ש המכסה אני.

Regarding the test of the Akeidah it is written "and he saw [the place] from afar," etc. — for the Holy One tested him [Avraham] specifically in the middah (attribute) of yirah (awe), since his essential middah was ahavah (love) and closeness, as it is written "Shall I conceal [from Avraham what I am doing]?"

The Sefas Emes explains that Avraham's defining attribute was ahavah — a relationship of love and intimacy with Hashem, reflected in Hashem's reluctance to hide anything from him. The Akeidah, however, came to test him precisely in the opposite middah, yirah, which is why the verse describes him seeing the place "from afar" — at a distance.

ועתה הי' מרחוק בבחי' היראה לכן נאמר ירא אלקים אתה וכ"כ ה' יראה כו' שבא עתה למדת היראה לכן לא ייחס הנסיון ליצחק כי זה הי' מדתו ואין זה נסיון כי בודאי הי' כ"א מדה שלו בשלימות.

And now he was "from afar," in the aspect of yirah; therefore it is said "[now I know that] you are one who fears Elokim," and so too "Hashem yireh (will see)," etc. — that he now arrived at the middah of yirah. Therefore the test was not attributed to Yitzchak, for this [yirah] was his [Yitzchak's] own middah, and that is no test, since surely each one possessed his own middah in completeness.

Because the Akeidah lifted Avraham into the attribute of yirah, the verses speak of "fearing Elokim" and "Hashem yireh." The test was Avraham's, not Yitzchak's, because yirah was already Yitzchak's natural middah — and one's own native attribute presents no test. Each of the Avos already possessed his own characteristic middah perfectly.

אבל עיקר הנסיון בבחי' אחרת כנ"ל:

Rather, the essence of a test lies in a different aspect [than one's own middah], as above.

The real nisayon (test) is always to rise in a dimension that is not one's natural strength — for Avraham, the man of love, that meant ascending in yirah.

Summary: Avraham's defining middah was ahavah — love and closeness to Hashem — so the Akeidah came to test him specifically in the opposite attribute of yirah, which is why he saw the place "from afar" and why the verses speak of "fearing Elokim" and "Hashem yireh." The test was Avraham's and not Yitzchak's, because yirah was already Yitzchak's own perfected middah, and a true nisayon lies precisely in rising within the dimension that is not one's natural strength.