It won't necessarily harm anything (at least on a 3 wire motor) that I know of, it will just spin the wrong direction. Or it will chatter vs spin.When you say make sure the wires are connected properly to the motor, how does one know which goes to which?
I've heard they could be connected any way and it should at least still work.
I found out ABC really matters on a sensored setup. Thought my MMX/2200kv was broken, then noticed I had ACB (I didn't notice the markings on the motor). Once I plugged it in proper, it stopped chattering and spun. With a non sensored, I think it just spins backwards if they are wrong.