That's kind of a shitty saying. We all make mistakes but the way that's phrased makes it sound unforgivable. The ramifications of hiring are bigger than your everyday mistake but it still happens.
The ramifications of hiring are bigger. Sometimes a firing is because of the individuals lack of performance, but I think this quote is asking the hirer to be mindful of what outcomes (layoffs) come from mistakes of their decision making.
Otherwise, it is a reminder that it is a failure to hire someone that doesn't work out, and a failure to not be able to use someone as most people have some skills and firing someone is a very harsh thing to do both to the ex-employee in their ex co-workers.