That's a tough question. I'm not quoting Marx above, I'm casually using intuition and memory. Honestly if I were strictly going off of Marx directly I wouldn't have talked so casually about the "full value of their work" since Marx draws a distinction between labor power (the commodity sold by the worker to the capitalist), living labor (work as it is actually performed) and dead labor (i.e. the products of past labor, including means of production). But yeah. This is mostly stuff you can find explained much better in Volume 1, Wage Labour and Capital, Value Price and Profit, and maybe a little bit of Volume 2.

If you want a full citation I'd have to put in some time and frankly it's the Saturday before Christmas and I'm feeling very lazy lol