Graduated path to mesirus nefesh

את בנך יחידך כו' פרש"י לתת שכר על כל דיבור וקשה מה תוספות שכר בזה.

"Your son, your only one..." — Rashi explains that this was to grant reward for each and every expression; but it is difficult: what added reward is there in this?

At the Akeidah, Hashem stretched out the command ("your son, your only one, whom you love, Yitzchak"); Rashi says this was to give Avraham reward for each phrase. The Sefas Emes asks: how does drawing out the wording create additional reward?

אמנם ודאי אלה המדריגות כ"א יותר מחבירו ומקודם נתרצה לתת סתם בנו ואחר כך יחידו האהוב לו כו'.

Rather, surely these are levels, each one higher than the next: first he consented to give over simply his son, and afterward his only one, the one beloved to him.

Each added word represents a higher madreigah of self-sacrifice. Avraham first accepted giving up "his son," then the greater test of "his only one," then "the one he loved" — ascending step by step.

ואמת כי אבינו אברהם הי' שוחטו מיד אם הי' אומר לו תיכף את יצחק.

And in truth, Avraham Avinu would have slaughtered him immediately had Hashem said to him at once, "Yitzchak."

Avraham's mesirus nefesh was so complete that even had Hashem named Yitzchak outright from the start, he would have carried out the command without hesitation.

אך כי כל מעשה אבות הי' הכנה לבנים שפעלו במעשיהם שנוכל גם אנחנו להיות עושים כמעשיהם ומי שאינו זוכה מיד למסור כל נפשו אעפ"כ ע"י המדריגות מקודם נכנס באהבת הבורא מעט.

But all the deeds of the Avos were a preparation for the children, for through their deeds they brought it about that we too can act as they did; and one who does not immediately merit to give over his entire soul nevertheless, by means of the gradual levels, enters a little into the love of the Creator.

The Avos lived their nisyonos in stages in order to forge a path for their descendants. Because of this, a person who cannot reach full mesirus nefesh all at once can ascend gradually, entering bit by bit into ahavas Hashem.

וע"י שכבר חביב לו מצות ה' יכול אח"כ לגבור יותר נגד יצרו ולבוא למס"נ וז"ש רש"י לחבבו בעיניו ולכן נכתב בנך יחידך כו' נגד כל המדריגות שנמצא במס"נ של בנ"י וכולם על ידי הכנת האבות כנ"ל:

And since the mitzvos of Hashem have already become beloved to him, he can afterward prevail more strongly against his yetzer and arrive at mesirus nefesh — and this is what Rashi means, "to make it beloved in his eyes." Therefore it is written "your son, your only one," corresponding to all the levels of mesirus nefesh found among Bnei Yisrael, all of them by means of the preparation of the Avos, as explained.

Once Hashem's mitzvos have become dear to a person, that very love empowers him to overcome his yetzer hara and reach genuine self-sacrifice. The drawn-out wording of the Akeidah thus corresponds to every gradual level of mesirus nefesh available to Bnei Yisrael — each one made possible by the groundwork the Avos laid.

Summary: The Torah stretched out Hashem's command at the Akeidah not because Avraham needed the gradual ascent — he would have given Yitzchak at once — but to embed within the Avos' deeds a graduated path of mesirus nefesh, so that their descendants who cannot reach full self-sacrifice immediately can enter the love of Hashem step by step and ultimately prevail over the yetzer hara.