Musar zu Schoftim 6:25

A person must purify his heart before he commences to pray (Shemot Rabbah quoted by Menorat HaMa'or page 39). We also find that Job referred to the fact that "there is no injustice on my palm, my prayer was pure." Rabbi Joshua the priest, son of Nechemyah queries how a prayer could be עכורה, murky, dirty. He concludes that the statement about Job's prayer not having been offered with hands soiled with violence does not refer to hands that are physically dirty but to the stains caused by sin. A person who has not first removed sin from himself calling upon G–d is not likely to be answered. Gideon, who was descended from the tribe Manasseh, excelled in those two attributes. He demonstrated this even before he destroyed the altar dedicated to the idol Baal and by subsequently building an altar for G–d and sacrificing on it (Judges 6:25-28).