This is from the Zohar (Parshas Kedoshim, 85a) quoted by the Kav Hayashar (Ch 14)
Come and see what is written in the Zohar (Kedoshim, 85a) regarding one who withholds the wages of a worker and does not pay him. His punishment is particularly great because a worker puts his very soul into his labor and his craft, therefore when his employer withholds his wages it is as if he is holding captive the soul of the worker as well as the souls of his entire household.
Every breath that comes out of the worker’s mouth as he engages in his craft – for it is usual for a worket to breathe heavily while he works – ascends before Hakadosh Baruch Hu. That night the souls of the worker and the members of his household, who are dependant upon those breaths, ascend before Hashem. Hashem then sees that those breaths were not remunerated for their efforts. In consequence, even if much blessing and success had been decreed for the employer, it is all taken away from him. Moreover, his own soul is no longer allowed to ascend On High each night, all because he withheld from his worker his wages. This iniquity also causes the employer’s life to be shortened, Rachmana Litzlan.
For this reason Rav Hamnuna HaZaken was accustomed to pay his workers their wages the moment they finished their tasks, saying to them, “Take back your soul that you deposited with me.” Even if the worker said to him, “Let it remain in your safekeeping,” he would refuse, saying, “It is not fitting that you should deposit even your body in my care, let alone your soul. This deposit should only be left in the care of Hakadosh Baruch Hu, as it is written, ‘BeYadcha Afkid Ruchi’ (Into Your hand I commit my spirit) (Tehillim 31:6).”
This should serve as a stern warning to people. If one hears one’s worker weeping over his labors, even if he is not Jewish – if he goes after his employer seeking the wages of his toil but the latter closes his ears, refusing to listen and telling him to come back another time – there can be no greater Chillul Hashem than this. His punishment will be swift in coming and his propert will be irretrievably lost.
Even if currently he enjoys a generous income, prosperity and success, it will not remain with him. Ultimately he will undoubtedly be impoverished and no one will take pity upon him. Many other afflictions are also brought about by this sim. Therefore one must be extremely careful not to stumble in the sin of withholding a worker’s wages.