Jesus answered by joining two commands from different parts of the Torah.
The first, Deuteronomy 6:4–5, was likely the most well-known passage in the Old Testament. Faithful Jews repeated it twice each day. It is called the Shema because it starts with the word Listen (Hebrew shema‘). This command matches the first part of the Ten Commandments (Exodus 20:2–11), which focuses on a person’s relationship with God.
God’s oneness is central to Jewish and Christian monotheism (belief in one God). It is the foundation for the command to love God fully—with all one's heart (thinking and affection), soul (desire and feeling), mind (understanding), and strength (energy and power).
The second command comes from Leviticus 19:18. It matches the second part of the Ten Commandments (Exodus 20:12–17), which concerns relationships with other people. This command is based on the natural tendency of people to care for themselves. Its importance in the early church is shown by how often it is repeated (Matthew 5:43–44; 19:19; 25:31–46; Romans 13:8–10; Galatians 5:14; James 2:8; Didache 1.2; 2.7).
These two commands are closely connected and together form one commandment. This connection rejects a mysticism concerned only with a person's relationship with God or a humanism concerned only with human relationships.