'On the Sabbath' in the Bible

Now they went on from Perga and arrived at Antioch in Pisidia, and on the Sabbath day they went into the synagogue and sat down.

and on the Sabbath day we went outside the city gate to the bank of the [Gangites] river, where we thought there would be a place of prayer, and we sat down and began speaking to the women who had come there.