What is the ruling on working until 8:00 p.m. after having made a covenant not to work after 7:00 p.m., and is it permissible to retract this covenant?

You are required to offer expiation for an oath (kaffarat yamin) if you break your oath that was accompanied by a covenant. It is permissible to retract it if you find something better, as the Prophet, peace and blessings be upon him, said: "If you take an oath, then see something better than it, then expiate for your oath and do that which is better." The expiation for an oath is feeding ten poor people, or clothing them, or freeing a slave. If you are unable to do any of these, then fast for three days. The expiation does not multiply by your saying "By Allah the Almighty" before your covenant, as this is merely an affirmation of the single oath.