Gemara: Due to the sin of not giving terumot and ma’asrot (tithes tokohanim and levi’im, respectively), the skies are prevented from giving rain and dew … If they give, they are blessed, as the pasuk says: "Bring the ma’aser to the storehouse, and it shall be food in My house, and test Me in this … if I will not open up the skylights of the heavens and pour out limitless blessing" (Malachi 3:10) – until your lips get worn out saying "enough."
Ein Ayah: A person’s affection for a mitzva is affected by his understanding of its purpose, which increases with his knowledge of the depths of the Torah and the ways of Hashem. This can be lacking in the realm of general lack of connection to Torah or in a more localized manner that relates to a specific mitzva, making him lax in fulfilling it.
The general deterioration is more serious, as it represents a darkening of the divine light in the world. The specific lacking for amitzva is less severe, but while it does not indicate a cursed status, it does not represent blessing. To fully appreciate a mitzva, the nation’s spiritual status must be excellent, and the general populous must be able to recognize the positive impact of holy people. When the proper outlook is strong, life improves dramatically.
Before a dangerous deterioration of people not giving ma’asrot, first a lack of appreciation of the impact of holy people and of the covenant of kehuna may weaken their enthusiasm to give. Even if a person does not reach the level at which he denies kohanim’s status, he might say that in his time it is not of value, as it will be obvious only in the Days to Come. So while he does not violate the laws, he looks for loopholes to obviate the need to give, a phenomenon the gemarabemoans (see Berachot 35b).
While this is not very destructive, as people follow the rules, it is far from a situation of blessing. Such a generation does not fully appreciate the true values of life and how the eternal spiritual needs (i.e., the place of kohanim and levi’im) transcend the situation in any specific era. The general level is a product of the cumulative service of many generations, which build "palaces" in the heaven and on earth based on embracing Torah and mitzvot in full vigor. It is not enough for people to comply with divine commands without sensing their greatness, the divine grace they contain, and their responsibility for the world’s development.
With a limited outlook, man can never have full satisfaction or success. How can an external blessing be valuable if he does not see the purpose of life? When life is not firmly settled, true blessing cannot take hold in the world. Each generation must elevate itself to a broad outlook that sees how the power of life must be cumulative over generations, and, in that way, emulate Hashem, Who is from the outset and is also with those of later generations (see Yeshaya 41:4). Then, even if the kohanim are not making an obvious impact in the present generation, they are still crucial due to their assured crucial role in the Time to Come, based on the connection built in the past, present, and future.
When things are viewed correctly, life deserves internal blessing, which can find expression in physical things as well. Not violating themitzvot of ma’asrot is not enough; one must make the effort to actually give with intention and love. The resulting blessing is wonderful. On one hand, it is in the physical world, while its foundation is general and internal. The blessing brings one to realize that life is intrinsically good even when it requires hard work.
Then man is ready for a blessing in which one continually says "enough." One can never have such satisfaction when his life is only focused on the present, as he will never be satisfied with what Hashem gave him. When received properly, the blessing fills one’s spirit, so that enthusiasm breaks forth externally (lips) as well, as an expression of internal emotion.