What is the primary theme of the Shema as expressed in Deuteronomy 6?

The primary theme of the Shema, as expressed in Deuteronomy 6, centers on the command to love God with all one's heart. This foundational text emphasizes the total devotion required in a relationship with God, urging believers to engage with their faith comprehensively—emotionally, physically, and spiritually. The Shema begins with the declaration of the oneness of God and immediately transitions into the call to love Him wholeheartedly.

This love is not merely an emotion but translates into actions such as teaching God's commandments to children, discussing His words in daily life, and living them out in the community. Such commands underscore the deep connection between love for God and ethical living, highlighting that true devotion impacts every facet of a person's life.

The other options, while relevant to religious practice, do not encapsulate the core message of the Shema as succinctly as the call to love God does. Obeying decrees, celebrating festivals, and following customs are important aspects of religious life, but they are secondary to the fundamental command to love God above all else.