Musar על סנהדרין 7:7

Our sages also add to that an additional rule: We learn from the singling out of a particular work-prohibition that if a person violates more than one of the 39 work-prohibitions on the Sabbath he is liable for a separate penalty for each one of such transgressions. The Yerusalem Talmud Sanhedrin 4,6 derives from the words "in all your dwellings," that no Court is to sit on the Sabbath.