This song was composed by Rabbi Baruch Chait, and is probably one of the most well known Chassidic songs in Jewish and Israeli culture today. The words are from Rabbi Nachman - כל העולם כולו גשר צר מאד והעיקר לא לפחד - the whole world is a narrow bride and the main thing is not to fear at all. We can remain fearless in the face of the greatest danger with our trust in God.