Most Christians can rattle off the answer to the question, “what is the greatest commandment?” That is to love God and love neighbor.
Or specifically, “The first is, ‘Hear, O Israel: The Lord our God, the Lord is one; and you shall love the Lord your God with all your heart, and with all your soul, and with all your mind, and with all your strength.’ The second is this, ‘You shall love your neighbor as yourself.’ There is no other commandment greater than these” (Mk 12: 29-31).