What did Henry David Thoreau mean when he said 'goodness is the only investment that never fails'?

Answer 1

This is NOT a professional answer, but in my opinion, what Henry David Thoreau meant when he said that is:

If you are good to people, it will never backfire in a negative way. If you invest yourself in something good, it will never fail.

Answer 2

Thoreau meant that being a good person and doing good deeds are valuable investments that will always bring positive returns in one's life, regardless of any external circumstances. Goodness and kindness towards others will always be beneficial and never lose their value.