This discourse was said by the Rebbe on Shabbat Mattot-Masey, 1966.  It concerns the concept of making vows, the subject of the beginning of the Sedra of the week, Sedra Mattot.

When a person makes a vow, they are generally forbidding themself from indulging in some physical pleasure. For example, a person might vow not to eat meat, or drink wine.  The Jerusalem Talmud asks: why make a vow, isn't it enough for you all the things the Torah forbids? Why forbid anything else?

The discourse explores the theme of our relationship with physicality and physical pleasures.  Ideally we should be able to relate to every aspect of the physical dimension of life, in order to elevate it.  But often a person can see this would be risky for them, because they can easily be dragged down i nto negative behaviour, so they have to be more circumspect.  The goal is the union of the physical and the spiritual.