Q. What is the most important commandment in the Decalogue?
A. I once put this same question to a group of students and one of them answered, “The most important one isn’t even there. It is ‘Thou shalt not get found out’.” The rest of the group made other, less facetious suggestions.
Strangely, no-one echoed what the commentator Nachmanides (the Ramban) said. His view was that the most important commandment was number 10 – “Thou shalt not covet”. He said that coveting, envying what belongs to other people, is the root of all the problems in human history.
People want other people’s houses, their fields, their money, their wives. It is bad enough when they think these thoughts; the really serious problem comes when the notion in their minds turns to action and it leads them to transgress the other commandments and to kill, steal, commit adultery and lie. If they took seriously their duties to God they would comply with their duties to their fellow human beings.
The Ramban explains that the reason the Ten Commandments in Ex. 20 are followed by Parashat Mishpatim with its civil and criminal legislation is that only with a Divinely-authorised legal code will a person be held back from coveting and turning the coveting from theory into practice.