Q. Can one use on Rosh Hashana a Shofar that belongs to a friend without permission these days?
A. On question 2662 we wrote: While blowing with a Shofar without permission from the owner may be questionable even bedieved (after the fact), if not for the concept that the mitzva is listening and not the blowing itself, also we assume that a person is pleased that someone else complies a mitzva with his property. (See Shulchan Aruch O.H. 586: 2, and Mishna Berura 9). Sefer Chasidim (771) rules that one who davens with a siddur that belongs to another without his permission, has to repeat his tefila; however, other Poskim disagree.
In the days when people are afraid of disease contamination one should not use someones Shofar without his permission as he may not comply even after the fact.
Rabbi A. Bartfeld as revised by Horav Dovid Pam, Horav Aharon Miller and Horav Chanoch Ehrentreu Shlit’a.