The statement of the gemara "מה ירא אלקים האמור באברהם מאהבה וכו", always bothered me. If Avrohom truly achieved a level of ahavas Hashem through the akeida then why does the pasuk say that "עתה ידעתי כי ירא אלקים אתה"?
What is the difference between ahava and yirah (we are not referring to fear of punishment rather awe of Hashem as rashi explains)? It seems that Tosafos tries to illustrate this idea by quoting the Yerushalmi of R' Akiva. יראה is apparent by one's actions, but אהבה cannot be shown by once actions only by their attitude. A ירא would act the same as an אוהב when faced with any challenge, whether it is the challenge of shechting his son, or giving his life for קבלת עול מלכות שמים like R' akiva. The difference is that one who only achieves יראה would rather have not been in the situation to begin with. But one who achieves אהבה is eager to be in a situation where they can demonstrate their commitment. R' Akiva's actions to give up his life does not demonstrate אהבה, but his attitude of smiling indicating that he was eager to be faced with the challenge truly demonstrates his אהבה.
The Meshech Chomchma points out on the pasuk "עתה ידעתי כי ירא אלקים אתה ולא חשכת את בנך את יחידך ממני", the pasuk conspicuously leaves out the term "אשר אהבת", why? He answers that the mal'achim don't know inner thoughts of a person -
ואהבה היא מכוחות הנפש הנסתרים מהנבראים זולת הבורא יתברך
Meaning, אהבה can never be determined by a persons actions, it is a reflection of attitude. That is why the angel that calls to Avrohom cannot conclude from Avrohom's actions that he is a אוהב, it can only conclude from his actions that he is a ירא אלקים. But the pasuk that refers to Avrohom as "זרע אברהם אוהבי" indicates that Avrohom's actions were controlled by an attitude of ahava. That is why the gemara considers both one who serves out of ahava and one who serves out of yir'ah, to be tzadikim gemurim, but their reward reflects their attitude.