The Tipiṭaka in Three Languages

Vibhaṅgasutta

Suttapiṭaka · Saṁyuttanikāya · Mahāvaggasaṁyutta · Vol. 19 · Section 1200

[1200] And what, bhikkhus, is investigation (vīmaṃsā) that is constricted internally? That investigation, bhikkhus, which is accompanied by dullness and drowsiness (thīna-middha), associated with dullness and drowsiness — this, bhikkhus, is called investigation that is constricted internally.

English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.

This passage also appears in 2 other places