Visuddhimagga VIII-72

Appanātoti appanākoṭṭhāsato kesādīsu ekekasmiṃ koṭṭhāse appanā hotīti veditabbāti ayamevettha adhippāyo.

（7）「以安止」──（三十二部分中）（于令生）安止（定）的部分（作意）当知即于发等的各各部分而坐起安止（定），为（安止定）的意义。

Ñ(VIII,72): 7. As to absorption: as to absorption part by part. The intention here is this: it should be understood that absorption is brought about in each one of the parts.