From Ohr Avigdor Shaar Bitachon by Rabbi Avigdor Miller
A person with bitachon (trust in Hashem) is actually a wealthy man. True wealth is when he puts his trust in Hashem. He knows that Hashem is going to do for him what’s right and therefore this man will live in a certain way that we’ll soon see, a certain life that’s different from the way other people live.
The effort to put bitachon in your mind gives you the greatest success in your life
That person, therefore, is considered a man who has wealth in his own home, as if he were an alchemist who manufactured gold and silver. We’re talking about people who live normally and are attempting to maintain themselves by some form of livelihood. They work and engage in business, but at the same time they’re working on the middah (quality) of having bitachon in Hashem.
Of the two things that they are doing (working on their livelihood and on their bitachon), which one brings them the most profit? The work on bitachon. A man can have a store or be a laborer who gets wages, but he should know that his real wealth is not what he puts in the bank. It’s what he puts into his mind. This is not so easy when we consider that the baal bitachon is working on his livelihood. He is exerting himself for his sustenance, and at the same time this man is laboring to put into his mind all the principles of trust in Hashem that we’re going to learn later. The author of Chovos Halevavos is telling us that of the two forms of effort, the effort to put bitachon in your mind is the one that’s really going to give you the final success in your life, not only in the World to Come, but in This World too.