The Sabbath

You will remember that the Ten Commandments were given by God to the Jewish people at Mount Sinai after they had escaped from Egypt.  The Fourth Commandment taught them that they must keep the seventh day of the week, the Sabbath, as a day on which no work, whether by people or animals, was to be done.  Some people make the mistake of thinking that the Sabbath is the same day as Sunday, but of course the seventh day is not Sunday but Saturday, and the Jews to this day still keep Saturday, the Sabbath, as a day of rest.

Sunday

Although the first Christians were Jews, the Christian Faith and the Christian Church were founded by Jesus for all the peoples of the earth, and so the Jewish Sabbath was not taken over.  Instead, from the very beginning the first day of the week, Sunday, was set apart by the Apostles as a day of worship and rejoicing in honour of the Resurrection of Jesus on Easter Day, the first day of the week.  And so you remember, on Low Sunday, the very first Sunday after the Resurrection, the Apostles all met together in the Upper Room in Jerusalem.