(Devarim 11:22) "For if you keep, keep, all of this mitzvah": What is the intent of this (repetition)? Scripture is hereby stressing that just as one must take care that his sela (a coin) not go lost, so must he take care that his learning not go lost. And thus is it written (Proverbs 2:4) "If you search for it (Torah) like silver, etc." Just as it is difficult to acquire silver, so it is difficult to acquire words of Torah. — But perhaps just as it is difficult to lose silver (i.e., silver is not readily broken), so it is difficult to lose Torah! It is, therefore, written (Job 28:17) "Gold and fine glass cannot be compared to it." It is as difficult to acquire them (words of Torah) as gold, and as easy to lose them as vessels of glass.