Long before Jesus was born, God made his will known to Moses. God’s will took the form of Ten Commandments and other laws, which Moses shared with God’s people.
“A lawyer once asked Jesus, ‘Sir, which is the most important command in the laws of Moses?’ Jesus replied, ‘Love the Lord your God with all your heart, soul, and mind.’ This is the first and greatest commandment. The second most important commandment is similar: ‘Love your neighbor as much as you love yourself.’ All the other commandments and all the demands of the prophets stem from these two laws and are fulfilled if you obey them. Keep only these and you will find you are obeying all others.” (Matthew 22:36-40)