The continuous repetition of sacred words such as god names, mantras, etc. is said to be a Japa.
Japa is so much powerful. It is crore times more powerful than Puja and Stotra. You can read more about the following from this answer
Stotra is equal to a crore of PujA. A Japa is equal to crore of Stotra. DhyAna is equal to a crore of Japah and one crore of DhyAna is equal to Laya.
So, it is necessary for a person to do Japa in order to improve herself. I came across the following verse recently saying that greatest sins can be removed by doing a Japa.
Japatho nasthi pathakam
But I cannot find the source scripture of the verse. What is the source of this verse?