[626] What is the power of serenity (samathabala)? Unification of mind (citta) and non-distraction through renunciation (nekkhamma) is the power of serenity. Unification of mind and non-distraction through non-ill will (abyāpāda) is the power of serenity. Unification of mind and non-distraction through the perception of light (ālokasaññā) is the power of serenity … Unification of mind and non-distraction through contemplating relinquishment (paṭinissaggānupassī) while breathing in is the power of serenity; unification of mind and non-distraction through contemplating relinquishment while breathing out is the power of serenity.
"The power of serenity": in what sense is it the power of serenity? Through the first jhāna it does not waver with regard to the hindrances (nīvaraṇa): thus it is the power of serenity. Through the second jhāna it does not waver with regard to thought and examination (vitakka-vicāra): thus it is the power of serenity. Through the third jhāna it does not waver with regard to rapture: thus it is the power of serenity. Through the fourth jhāna it does not waver with regard to pleasure and pain: thus it is the power of serenity. Through the attainment of the sphere of infinity of space (ākāsānañcāyatana-samāpatti) it does not waver with regard to the perception of form, the perception of repulsion, and the perception of diversity: thus it is the power of serenity. Through the attainment of the sphere of infinity of consciousness (viññāṇañcāyatana-samāpatti) it does not waver with regard to the perception of the sphere of infinity of space: thus it is the power of serenity. Through the attainment of the sphere of nothingness (ākiñcaññāyatana-samāpatti) it does not waver with regard to the perception of the sphere of infinity of consciousness: thus it is the power of serenity. Through the attainment of the sphere of neither perception nor non-perception (nevasaññānāsaññāyatana-samāpatti) it does not waver with regard to the perception of the sphere of nothingness: thus it is the power of serenity. It does not waver, does not shake, does not tremble with regard to restlessness, with regard to the defilements (kilesa) accompanied by restlessness, and with regard to the aggregates: thus it is the power of serenity. This is the power of serenity.
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.