Earning brachah through one's deeds

בפסוק בי נשבעתי כו' יען עשית הדבר הזה כו' ברך אברכך ארבה את זרעך כו'.

On the pasuk: "By Myself I have sworn" … "because you have done this thing" … "I will surely bless you, I will greatly multiply your offspring," and so on.

The Sefas Emes opens with the brachah Hashem gives Avraham after the Akeidah.

קשה כי אלה הברכות והבטחות כבר הבטיח לו הקב"ה קודם הנסיון ומה השכר.

This is difficult: for these brachos and promises the Kadosh Baruch Hu had already promised him before the nisayon, so what is the reward?

If Avraham was already promised all this earlier, the Akeidah seems to have earned him nothing new.

אכן זה השכר שיהי' לו כל אלה הברכות בזכות מעשיו ומקודם כתיב ויחשבה לו צדקה ואאע"ה ביקש שיהי' הכל עפ"י מעשיו.

However, this is the reward: that he should now have all these brachos in the merit of his own deeds — whereas previously it is written "and He reckoned it to him as tzedakah," and Avraham Avinu (alav hashalom) had asked that everything be according to his deeds.

Earlier the promises rested on Hashem's gift of righteousness credited to Avraham's emunah; now, after the Akeidah, the very same brachos are earned through his actions, which is what Avraham himself had wanted.

ואמת שמה שבא בזכות מעשה האדם הוא קיים לעד.

And it is true that whatever comes through the merit of a person's deeds endures forever.

That which a person earns through his own avodah has a permanence that an unearned gift does not.

וזה עצמו מה שביקש על הבנים אף שהאמין בהבטחתו ית' רק שזה הי' מבוקשו לזכות בעצמו לכל זה וז"ש יען כו' פי' בזכות מעשיך יהי' לך כל זה:

And this itself is what he requested regarding the children — even though he believed in His promise, may He be blessed; rather, this was his request: to himself become worthy of all this. And this is the meaning of "because" — i.e., in the merit of your deeds all this shall be yours.

Avraham fully trusted Hashem's word, yet he yearned to personally earn the brachah; the word "because you have done this" tells him that now the promises are his by right of his own deeds.

Summary: Although Hashem had already promised Avraham these brachos before the Akeidah, the reward of the nisayon is that he now merits them through his own deeds — and what a person earns through his avodah, rather than receiving as an unearned gift, endures forever.