(Bhagavad Gita 10:25)
I am the sacrifice of silent repetitions, says Lord Krishna in the Bhagavad-Gita.
English Commentary - Swami Sivananda
Manu has said: "Whatever else the Brahmana may or may not do, he attains salvation by Japa (silent repetition of a Mantra) alone."
Japayajna: There is neither injury nor loss in this Yajna. Therefore, it is regarded as the best of all Yajnas.