Our religion divides itself between two types of commandments, those between man and G-d and those that govern interpersonal relations.

Which is more important?

In other words if you were G-d would it be more important for a Jew to pray to you three times a day, eat Kosher food, fast on Yom Kippur or to love your fellow Jew and hence be charitable, kind, compassionate with all your heart and soul.

Until the advent of Rabbi Yisroel Baal Shem Tov people thought the former instead of the latter, the Baal Shem Tov and particularly the Alter Rebbe taught that the former is only for the sake of the latter.