My boss and I had an agreement for a salary. Now he is trying to get back from what we agreed upon in all kind of excuses. Is there anywhere in the Tanach that it says that one should not deceive his friend and needs to stand for what he promised?

At least twice in the Torah (Vayikra 19;13 and Devarim 24;14) the Torah specifically prohibits cheating the wage earner. There are numereous prohibitions concerning lying and reneging on agreements. However, not every statement of intent is binding. I would suggest you first cosult a halachic authority about the specific promises that were made, and then reapproch your boss.