Are My Tefillin (Still) Kosher?
When determining the kashrus of tefillin the most obvious issue is how often, if ever, should tefillin be opened for the parshios (writing) to be examined. Many are surprised to learn that the Shulchan Aruch (39:10) records that tefillin that are in regular use need not be checked as they have a continued chazaka (assumption) of being kosher. Nevertheless, the Mishna Berura recommends that the parshios be checked as they can potentially be ruined from sweat. The Aruch Hashulc