the Six Constant Mitzvot

There are six mitzvos that Jews are instructed to fulfill at all times and in all places. 

Mitzvos are generally classified into two categories, time-bound and not time-bound. Time-bound mitzvos can only be fulfilled at certain times, such as eating matzah on Pesach or shaking a lulav on Succos. Even most mitzvos that are not time-bound cannot be fulfilled all the time. For example, one cannot fulfill the mitzvah of mezuzah if one doesn’t have a door. There are, however, six mitzvos that Jews are instructed to fulfill at all times and in all places. 

edited from Rabbi Jack Abramowitz