Jesus said that the 2 greatest Commandments are From Matthew 22:36-40 New International Version
36 “Teacher, which is the greatest commandment in the Law?”
37 Jesus replied: “‘Love the Lord your God with all your heart and with all your soul and with all your mind.’[a] 38 This is the first and greatest commandment. 39 And the second is like it: ‘Love your neighbor as yourself.’[b] 40 All the Law and the Prophets hang on these two commandments.”
In the old testament can be found in Exodus 20 the 10 commandments