The Tipiṭaka in Three Languages

Rahogatavagga

Suttapiṭaka · Saṁyuttanikāya · Mahāvaggasaṁyutta · Vol. 19 · Section 1268

[1268] He dwells contemplating the mind in the mind (citta) internally … contemplating the mind in the mind externally … contemplating the mind in the mind both internally and externally — ardent, clearly comprehending, mindful, having removed covetousness and grief regarding the world.

English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.

This passage also appears in 5 other places