[21b bottom] Rava: One may not immerse vessels within other vessels (at least for Hekdesh) because the Rabbis issued a decree so that a person should not come to immerse needles and spinning hooks within a vessel whose opening is not at least the size of a skin-bottle’s tube (the spout of a leather bag for holding liquid was a small standard size).
T’s Lesson: Make sure not to go by the minimum amount involved in a Mitzvah. Just as the opening of this leather bag was the least required (but ideally it should be bigger), so too our mitzvah observance should not go by the lowest required level. We should always strive for much greater amounts (do not learn just five minutes a day, try for at least an hour a day!). If we try to make it happen, Hashem will help us succeed.