Yuganaddhavaggasuñakathā

Suttapiṭaka · Khuddakanikāya · Paṭisambhidāmagga · Vol. 31 · Section 646

[646] What is external emptiness? External forms (rūpa) are empty … external dhammas are empty of self, of what belongs to self, of what is permanent, of what is stable, of what is everlasting, of what is not subject to change. This is external emptiness.

English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.

This passage also appears in 1 other place

Vol. 31 · Section 635 — Yuganaddhavaggasuñakathā