Blow the shofar (ram's horn) at the new moon, and again at full moon to call a festival!
There are times when, like at the time of the new moon, we are in the dark, we are afraid, we do not know what is going to happen. At those moments we need to wake us up to what we need to do at that moment so we can let go of the habits and behaviors that keep us separated from God and humanity. The shofar reminds us to be conscious that we are part of the Divine one-ness of the universe and so we need not be afraid of the dark.
The sound at the shofar at both times call us back to our Source, to the One. Each does this in its own unique way, but each is just as essential living a life filled not only with laws and rules, but with joy, celebration and gratitude.