Visuddhimagga XXIII-21

Kenaṭṭhena samathabalaṃ? Paṭhamajjhānena nīvaraṇe na kampatīti samathabalaṃ. Dutiyajjhānena vitakkavicāre…pe… nevasaññānāsaññāyatanasamāpattiyā ākiñcaññāyatanasaññāya na kampatīti samathabalaṃ. Uddhacce ca uddhaccasahagatakilese ca khandhe ca na kampati na calati na vedhatīti samathabalaṃ. Idaṃ samathabalaṃ.

止力是什么意义？即以初禅而于诸盖不动故为止力；以第二禅而于寻伺……乃至以非想非非想处定而于无所有处想不动故为止力。于掉举、与掉举相共的烦恼及诸蕴不动不摇不震荡故为止力。这便是止力。

Ñ(XXIII,21): 'In what sense is serenity a power? Owing to the first jhana it does not waver on account of the hindrances, thus serenity is a power. Owing to the second jhana it does not waver on account of applied and sustained thought, thus serenity is a power ... (etc.) ... Owing to the base consisting of neither perception nor non-perception it does not waver on account of the perception of the base consisting of nothingness, thus serenity is a power. It does not waver and vacillate and hesitate on account of agitation and on account of the defilements and the aggregates that accompany agitation, thus serenity is a power. This is the serenity power.