Shiva Purana
मंत्राभ्यासवशेनैव मंत्रवाच्यार्थगोचरः ॥ अव्याक्षेपा मनोवृत्तिर्मंत्रयोग उदाहृतः ॥ ८ ॥
The concentration of the mind without disturbances, on the expressed meaning of the mantra along with the practice of the mantra is mantrayoga.
english translation
maMtrAbhyAsavazenaiva maMtravAcyArthagocaraH ॥ avyAkSepA manovRttirmaMtrayoga udAhRtaH ॥ 8 ॥
hk transliteration by Sanscript