1,155. When Rosh Hashana Falls on Shabbos

Hilchos Shofar, Succah v’Lulav 2:6

If Rosh Hashana falls on Shabbos, the shofar is not blown anywhere even though it is only prohibited by rabbinic enactment. It would be appear proper for blowing shofar - a Torah obligation – to supersede rabbinic legislation but, nevertheless, the shofar is not blown out of concern that one person may deliver a shofar to another and it will come to be carried four cubits through the public domain or transferred from one type of domain to another, violating Shabbos prohibitions, which are capital offenses. We can expect that transferring a shofar would inevitably occur because everyone is obligated to hear the shofar but most people are not skilled in blowing one.

Hilchos Shofar, Succah v’Lulav 2:7

Children who have not yet reached the age of education in mitzvos need not be prevented from blowing shofar on a Shabbos that is not Rosh Hashana so that they will learn the skill. An adult may instruct children in blowing the shofar on Rosh Hashana, whether they have reached the age of mitzvah education or not, because blowing shofar is only prohibited by rabbinic enactment.