G-d appeared to him that night and said, “I am the G-d of your father Abraham. Do not be afraid, for I am with you. I will bless you and make your descendants numerous for the sake of My servant Abraham.”
Genesis 26:24
Notwithstanding Isaac’s own substantial merits, it was only in the merit of his father Abraham that G-d assured him of success in life.
In the Temple service, the merit of the patriarchs was mentioned every day before the morning sacrifice, and we mention them in the opening paragraph of our daily prayers. This teaches us how important it is to constantly remember that we do not live in a spiritual vacuum; our lives are the continuation and fulfillment of the lives of those who have come before us, paving the way for us with their inspiration and accomplishments. The Torah itself tells us that we will be redeemed in the merit of the patriarchs.
Similarly, when we strive to be worthy descendants of all our holy ancestors – studying their teachings, following their examples of holy behavior, and abiding by their ethical instructions in order to forge our own relationship with G-d – their merit protects us from harm and ensures us of receiving G-d’s blessings in the fullest measure.
--Daily Wisdom Vol. 3