In the Babylonian Talmud we find that the shofar was blown every Friday, at the close of the day.
The academy of Rabbi Yishmael taught: On Friday afternoon we sound six shofar blasts announcing the arrival of the Sabbath.
Rabbi Yishmael was a Tanna from the third Tannaitic generation. His studied with Rabbi Akiva. After their deaths, the disciples of these two Torah giants continued their learning in the name of their famous teachers.
The Tanna (“repeaters” or “teachers”) were the Rabbinic sages whose views are recorded in the Mishnah, from approximately 10 CE-220 CE, a time span also referred to as the Mishnaic period, lasting about 210 years. The first shofar sound summoned those who are working in the outer fields to return to their homes to welcome the Sabbath. These distant workers would then meet the workers in the more proximate fields to enter the town together.
The second blast is an order for commerce to cease to welcome the Sabbath. At home, hot water would be heating in pots.
The third blast instructed that the pots be removed from the fires and the food should be insulated for the next day’s meal.
After the third blast, the Baal Tekiah (shofar sounder) would wait the the amount of time needed to roast a small fish over a fire, or to attach bread dough to the oven walls.
As a final alarm, the shofar sounder (who is attached to the synagogue) ends his blasts with a Tekiah, Teruah and another Tekiah ushering in the Sabbath.
Thus we have six blasts paralleling the number of work days in the week. On the seventh you shall rest.
This article was based on material provided by Arthur Finkle