In our daily prayers we say that God "does the will of those who fear Him." As our Sages teach, "A tzaddik (righteous person) decrees — and God fulfills". They also state, " Anyone who has a sick person in his household should go to a chacham (a wise person) to pray for him. "
Grand Rabbi Levi Yitzchak Horowitz (the "Bostoner Rebbe") said that a Chassidic Rabbi is in many respects like a plumber. God wants only to bestow goodness upon us, and all a person needs to do is make himself into a vessel to receive the good. But our bad deeds "jam up" the pipes through which Divine goodness flows. A tzaddik has the ability to "unclog" these pipes for the person.
A righteous person has a power of prayer more than most of us. Torah scholars (Chassidic or not) who have virtually perfected their character are known to have such powers. Until his passing several decades ago, many tens of thousands flocked to Rabbi Yaakov Yisrael Kanievsky (the "Steipler") for his blessing.
It's known that prior to their highly dangerous but successful air strike on the Iraqi nuclear reactor in 1980, the Israeli pilots appeared before the Steipler and asked for his blessing. He told them "go in peace and return in peace."
Sources:
- Psalms 145:19
- Bava Batra 116a
- Ta'anit 23a
