We all know that Warren Buffett is a quote machine for his simple and yet profound wisdom.

Naturally, much of it has to do with investment, but as he approaches 90, Buffettis uniquely qualified to impart life advice that could change the course of careers and businesses.

Buffett has no shortage of advice about the importance of finding integrity in leaders. He’s been telling us for a while that, of all the decisions we make in life, one of the most important ones is to invest in relationships with honest and ethical people.

Who should you invest in?

To further drive home the point that success comes from those you surround yourself with, he once asked University of Florida students to think of a classmate they felt had the makings of success long term, such that they would want to get 10 percent of that person’s earnings for the rest of their lives. Here’s what he said:

You would probably pick the one you responded the best to, the one who has the leadership qualities, the one who is able to get other people to carry out their interests. That would be the person who is generous, honest, and who gave credit to other people for their own ideas.

Sounds to me like Buffett has been reading a few servant leadership books. Let’s break his advice down into why we should seek to invest in leaders with traits such as generosity, honesty, and giving credit to others.

1. They are selfless.

A leader who manages through self-interest will naturally view others as objects and a means to that end. This mindset is dictated by ego. Selfless leaders, on the other hand, don’t eliminate the ego; rather, they harness the ego in healthy and constructive ways to benefit other people. In the words of the Dalai Lama, we must make sure “it is a serving ego and not a deserving ego.”

2. They acknowledge the contributions of others.

While leaders in top tiers of an organization may be more apt to acknowledge the glorified contributors who help make their companies profitable, a leader Buffett advises us to invest in will praise and recognize all human contributors who make a difference, from the mail room to the board room.

3. They display honesty through vulnerability.

Vulnerability in the workplace is often vilified as soft and inappropriate. On the contrary, vulnerability is about building trust — the backbone of successful leadership. The best leaders are catching on to the idea that when employees feel safe and open to express their ideas and differences of opinion, as well as their failures and even fears, they are emotionally engaged with their work. This is good for performance.

4. They show generosity by valuing people’s time.

Bringing this full circle to acknowledge one of Buffett’s greatest strengths, his good friend, Bill Gates, the second-richest person on the planet, gives Buffett, the third-richest, full credit for one basic life lesson that has led to his own success: “No matter how much money you have, you can’t buy more time,” writes Gates. “There are only 24 hours in everyone’s day. Warren has a keen sense of this. He doesn’t let his calendar get filled up with useless meetings.” Setting the right priorities creates margin for Buffett to spend more time with his close advisers and the people who matter most to him, like Gates. “He’s very generous with his time for the people he trusts,” says Gates.

Originally published on Inc.

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