Working on Friday Afternoon
From Halachipedia
Working Friday Afternoon
One should not work on Friday afternoon past 9.5 hours into the day (Mincha Ketana). The reason is debated. One opinion holds that it's because we want to prevent one from transgressing the laws of Shabbos if he runs too late, and the other opinion says the reason is to leave time to prepare for Shabbos. While there are various leniencies (mentioned below), a G-d fearing person should do his best to abide by this Law. One who unrightfully does not abide by this law will not gain from the work he does after 9.5 hours into the day.
