In the book of Mishlei it is written: One with a good eye will be blessed (Mishlei 22:9). Our Sages say, do not read it: will be blessed [יְבֹרָך] but “he shall bless [יְבָרֵך].” That is, a good person always blesses others. And one who blesses Jews receives blessing himself, as is written, I shall bless those who bless you (Bereishis 12:3). Therefore, it is proper for every individual to always try to bless other Jews, for it might be a time of Heavenly good-will and the blessing will be fulfilled. For the same reason, one who receives a blessing from someone else, should respond, “And the same for you.” Even if the blessing is not fulfilled, it is nevertheless pleasing to the Creator, for it is good in the eyes of Hashem to bless Israel, and so it is counted as a mitzvah for the person.
One should always seek blessings from others and flee from quarrelling with anybody, which would bring curses upon himself. For our Sages taught: “Let not the blessing of an ordinary man be lightly esteemed in your eyes… and let not the curse of an ordinary man be lightly esteemed in your eyes” (Megillah 15a) — since there are moments of Divine good-will and there are moments of Divine anger.
In particular, one should seek the blessing of Torah scholars and tzaddikim, for their blessings are most likely to be fulfilled. And even if it is not fulfilled, he nevertheless receives blessing from Hashem for being a person who values Torah and righteousness, and he is counted among those who honor the Torah and its scholars. Conversely, a Torah scholar should be “One with a good eye shall bless,” so he should bless anyone who wishes a blessing from him, for he loses nothing by giving them and it gives pleasure to others. This counts as a mitzvah for him!
The Zohar teaches that when a person wishes to bless his fellow or his son, he should first bless the Holy One, blessed is He, and if the person does not do so, the blessing is not fulfilled.