Yirah is the gateway to ahavah
Chayei Sarah · ahavah · yirah · Avraham · Yitzchak
בפסוק ויתן כל אשר לו ליצחק.
On the pasuk: "And he gave all that he had to Yitzchak."
Avraham bequeathed everything he possessed to Yitzchak — which the Sefas Emes reads on a deeper, middah-level.
ע"פ הידוע שאאע"ה לקח לו מדת האהבה ויצחק מדת היראה.
Based on what is well known, that Avraham Avinu took for himself the attribute of ahavah (love), and Yitzchak the attribute of yirah (awe).
Each of the Avos embodied a spiritual trait: Avraham is love of Hashem, Yitzchak is fear and awe of Hashem.
עכ"ז ע"י היראה יכול אדם לבוא לאהבה ז"ש ויתן אשר לו ליצחק:
Even so, through yirah a person can come to ahavah — and this is the meaning of "he gave what he had to Yitzchak."
Avraham's own attribute, ahavah, was "given over" to Yitzchak's path of yirah, teaching that fear of Hashem is the gateway through which one reaches true love of Hashem.
Summary: Avraham embodied love and Yitzchak embodied awe; when the Torah says Avraham gave "all that he had" to Yitzchak, it hints that his attribute of ahavah was entrusted to the path of yirah — for it is specifically through yiras Shomayim that a person ultimately arrives at genuine love of Hashem.