Ajjhattikaduka

Abhidhammapiṭaka · Paṭṭhāna (4) · Vol. 43 · Section 281

[281] An internal phenomenon (ajjhattika dhamma) is a condition for an internal phenomenon by postnascence condition (pacchājāta-paccaya): the postnascent (pacchājāta) internal aggregates (khandhā) are a condition for this prenascent (purejāta) internal body by postnascence condition. The root should be done: the postnascent internal aggregates are a condition for this prenascent external (bāhira) body by postnascence condition. The root should be done: the postnascent internal aggregates are a condition for this prenascent internal and external body by postnascence condition. Thus all nine questions should be done. … is a condition by repetition condition (āsevana-paccaya): nine questions should be done.

English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.

This passage also appears in 3 other places