The One Commandment
The Ten Commandments are taught at a young age as a way to live rightly. They’ve even gone beyond the religious sphere and into popular culture such that just uttering the words “thou shalt not…” and then finishing the phrase with any set of instructions can give either a serious or humorous level of extra gravity to the instructions. We love our rules and we love to hate our rules, and we have a lot of them.
When I was in seminary, I remember that my teacher said that there were over 600 commandments listed in the Old Testament. This factoid was used to highlight the impossibility of keeping all of them with exactness and the need for grace because none of us could measure up on our own. It was also used as a jumping-off point to a discussion of the words of Jesus when He outlined the two great commandments.
When Jesus was asked what the greatest commandment was, he responded:
Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. This is the first and great commandment. And the second is like unto it, Thou shalt love thy neighbor as thyself. On these two commandments hang all the law and the prophets.Matthew 22:37-40
The phrase “the law and the prophets” is a term of art that refers to the majority of what we now call the Old Testament.  So, basically, Jesus was distilling all scripture extant at the time to a two-fold instruction to love God and love one’s neighbor – and that loving one’s neighbor is like unto loving God.
This is explained further in other parts of the New Testament. Jesus teaches that whatever we do to others – such as feeding the hungry, clothing the naked, visiting the sick, etc. – is the same as doing it to Him.  And the apostle John gets even more clear when he says “If a man say, I love God, and hateth his brother, he is a liar: for he that loveth not his brother whom he hath seen, how can he love God whom he hath not seen? And this commandment have we from him, That he who loveth God love his brother also.” 
So in the end, instead of hundreds, ten, or even two, we have only one commandment as Christians. Love our neighbors.
The simplicity of this commandment obscures how challenging it can be. It’s the work of a lifetime. It can feel a lot easier to live by a list of “thou shalt nots” instead of to live by a principle of love. It requires us to evaluate our motivations for everything we do. But in the end, it’s the only way to become like God, because God is love. “The Law” is the first five books of Moses. “The Prophets” refers to most of the rest of the Old Testament, with the exception of poetic books such at Psalms, Proverbs, Ecclesiastes, and the Song of Solomon.
 see Matthew 25:34-40
 1 John 4:20-21