In Bechukosai (26:42),
וְזָכַרְתִּי אֶת בְּרִיתִי יַעֲקוֹב וְאַף אֶת בְּרִיתִי יִצְחָק וְאַף אֶת בְּרִיתִי אַבְרָהָם אֶזְכֹּר וְהָאָרֶץ אֶזְכֹּר
and I will remember My covenant [with] Jacob, and also My covenant [with] Isaac, and also My covenant [with] Abraham I will remember. And I will remember the Land
Why are the forefathers written out of order?
The rebbe says that chazal taught us that the world stands on three things; Torah study, the service of Hashem, and kind deeds. Each father was known for one of these traits. Yaakov embodied Torah study, Yitzchak represented service of Hashem, and Avraham was the paradigm of the trait of kindness. The order of the fathers in the pasuk corresponds to the order utilized by chazal to enumerate the three things which the world depends on-- Torah, service of Hashem, then kindness.
What are other reasons that their names are written in this order? What is the significance of stating the names of Avraham, Yitchak, and Yaakov?