Siman 142

(14.) When he came from the Land of Israel he said along the way: "On this journey I fulfilled the entire Torah in all its aspects — for I attained the fulfillment of the entire Torah, so that even if I were sold to an Ishmaelite in distant lands where there is no Jew, and he sent me to tend animals, and even if I did not know when Sabbath or Festival is, and I had no tallis or tefillin and no sukkah and no other commandment etc. — even so I would be able to fulfill the entire Torah in its entirety." And this is already explained elsewhere [Shivchai HaRan, 22].