“Make thy gold multiply.”

Why it was said

In The Richest Man in Babylon, George S. Clason has Arkad teach seven cures for a lean purse to the men of the city. This is the third. Having learned to keep at least a tenth of what they earn and to control their spending, his students are told to put the saved money to work.

What it actually means

Saving, in Clason's parable, is only the first step. Gold kept in a purse stays the same size; gold put to work earns more gold, and those earnings can be put to work in turn. Arkad's lesson is an early, plain description of compounding. The cure comes paired with the next one, guarding the treasure from loss, which warns against chasing high returns in ventures one does not understand. Read together, they make a modern point in old language: invest steadily in things you understand, let the returns reinvest, and treat the safety of what you put in as part of the return. The parable is set in ancient Babylon and was written in the 1920s, but the arithmetic is the same for an index fund today.

How to use it

1. 1Set up an automatic monthly transfer from your savings into a diversified investment, and leave the returns reinvested.
2. 2Before any investment, write one sentence explaining how it makes money; if you cannot, treat that as a reason to wait.