As part of my personal development toward being a Benedictine oblate, I'm reading an edition of the Rule of St. Benedict with commentary to make it applicable to fathers, but I am considerably amazed how often the Rule is applicable to my work at Automattic.
For example, St. Benedict, in telling the qualities of an abbot, touches on preconceived biases and provides a solid rule for me to follow as a team lead.
Let him make no distinction of persons in the monastery.Rule of St. Benedict, Chapter 2
Let him not love one more than another,
unless it be one whom he finds better
in good works or in obedience.
Let him not advance one of noble birth
ahead of one who was formerly a slave,
unless there be some other reasonable ground for it.
Within the context of a monastery, this section demands that an abbot treat everyone equally and let that person's work speak for itself. At work, this is a reminder of the same. No matter if I get along better or worse with someone in particular or if a person has a good or bad reputation, a leader must treat everyone with equal footing. Any judgements of a person should be limited to a judgement of their actual work.
This sounds obvious and easy, but it is just as easy to get swept up enjoying the company of a particular employee and find yourself letting him or her off the hook for missing a performance benchmark unjustly or being annoyed with an employee for something minor and silly and let that influence you on their next evaluation.
While there are few people of noble birth or former slaves in our midst, we can promote or demote people in my minds by judging them based on their background, not their portfolio—"they went to Yale so they would be well-suited for this". Quite often, we do this without thinking about it, which therein lies the rub.
In leadership, whether that is of a household, of a monastery, or of a corporate team, some of our most damaging actions take place only because we aren't fully thinking through our preconceived biases.