Parshas Matos discusses a person who makes a neder (vow) and must keep what he says, unless it is absolved. Although in many situations vows are not viewed positively, we have an entire structure set up in order to put vows in place for Bnei Yisroel as whole. Our chachamim (sages) set up protective fences, a sort of "communal vow" so that we will not come close to sin. This stems from a love of Hashem and desire to do what He wants beyond merely following the letter of the law. This positive sense of ahava (love) brings us closer to Him, through the boundaries that our chachamim set up to protect the laws of the Torah.