Visuddhimagga XVI-82

 Tassevaṃ vāyamato taṃsampayuttova micchāsativiniddhunano cetaso asammoso sammāsati nāma. Sā upaṭṭhānalakkhaṇā, asammussanarasā, micchāsatippahānapaccupaṭṭhānā. 

（七）那如是的精进者的──与彼（正精进）相应，除去邪念的心不忘失为「正念」；注意是它的特相，不忘失是它的作用，舍断邪念是它的现状。

Ñ(XVI,82): When he exerts himself thus, the non-forgetfulness in his mind, which is associated with that [right view], shakes off wrong mindfulness, and that is called right mindfulness. It has the characteristic of establishing. Its function is not to forget. It is manifested as the abandoning of wrong mindfulness.