The performance of good actions gives rise to merit (punna), a quality which purifies and cleanses the mind. If the mind is unchecked, it has the tendency to be ruled by evil tendencies, leading one to perform bad deeds and getting into trouble. Merit purifies the mind of the evil tendencies of greed, hatred and delusion. The greedy mind encourages a person to desire, accumulate and hoard; the hating mind drags him to dislike and anger; and the deluded mind makes one become entangled in greed and hatred, thinking that these evil roots are right and worthy. Demeritorious deeds give rise to more suffering and reduce the opportunities for a person to know and practise the Dhamma….
~Venerable K. Sri Dhammananda Maha Thera