Japa is the spiritual practice of repeating a sacred word referring to the Divine. Such a sacred word can be a verse, a short prayer, a phrase or a mystic syllable. The purpose of the repetition is to bring the mind to a state of devotion and concentration. The practice of japa is as old as religion itself. Faith in the purifying and transforming power of such sacred words is a vital part of all religious traditions. These holy names can be called "key words." Every religion has such key words that inspire its followers: words charged with the power of holiness because many saints and prophets achieved God-consciousness by chanting or repeating them. When a seeker repeats such a word with faith and fervor, it releases the power of holiness, which fills his mind with devotion and then leads it to concentration, absorption, and illumination.
— Swami Adiswarananda, Meditation and Its Practices