"On that day you shall give his payment..." (Devarim 24:15)
We are obligated to pay our workers on time.
The Rambam teaches that withholding payment is considered like bloodshed
(Hilchos Sechirus 11:2). The Meshech Chochmah (on the above verse)
teaches that paying a worker on time is a greater mitzvah than giving
tzedakah because it is providing the person's livelihood in the most
honorable way. The Chafetz Chaim teaches that one should pay a worker on
time with the same commitment and dedication that he fulfills the mtizvos
of tefillin, mezuzah, or shofar (Ahavas Chesed, sec. 1, prefact to ch. 9).