Shema Yisrael (or Sh'ma Yisroel or just Shema) are the first two words of a section of the Torah (Hebrew Bible) that is used as a centerpiece of all morning and evening Jewish prayer services and closely echoes the monotheistic message of Judaism. It is considered the most important prayer in Judaism, and its twice-daily recitation is a mitzvah (religious commandment). Its main content is loving the one God with all one's heart, soul and might, and the rewards that come with this.
