Update: I expanded a bit on this as well.
I love to plug other developers, even for work that I could do. One of my favourite things to do is to help others succeed, and not just in development.
Over the years I've taught beginners skills in:
I taught beginners in kayaking after dropping 40 foot waterfalls on the weekend. I taught them because it often felt more fulfilling to see someone get their first roll, than it did for me to throw myself off a waterfall.
I taught kids (literally high school students) rock climbing locally. The day I got my first 5.12a climb, so did one of my students. I was way happier that she did it than I was that I did it.
A number of years back (which makes it decades in internet time) I recommended someone else as a great designer. At the time, I certainly needed the work but so did they. I distinctly remember getting chastised by another Twitter user with something to the effect of:
Why would you say that someone else does good work, they are your competitor? Just sell yourself.
On the surface that sounds like sound advice. I am in 'competition' for work with many of the people I talk to online and offline. In theory we are trying to get the same clients so we can pay our bills.
The reality is that every time I have plugged someone, or sent them work I've got something in return. Some day they have work that they just can't do, and the first person they look to as a referral is me.
Not only is there some financial benefit at some point, there is a benefit to me personally right away. I just feel great when I can give work to someone else. Helping them out becomes the highlight of my working week.
If you're not plugging other's, you should be. It's not going to affect your business in any bad way. It's going to turn around and give back to you.