Avraham Avinu builds three Mizbeachs. Rashi tells us that the first is to give thanks to God for promising him that he would have children and the Land of Israel. The second is to atone for the future sins of his descendants. However the last Mizbeach is a mystery, Rashi does not tell us why Avraham built a Mizbeach. 

In this shiur, based on a sicha from the Lubavitcher Rebbe, Rav Burg explains the three stages of love. Love because. Love despite. Love for no reason at all.