Vibhaṅgasutta

Suttapiṭaka · Saṁyuttanikāya · Mahāvaggasaṁyutta · Vol. 19 · Section 862

[862] And what, bhikkhus, is the faculty of concentration (samādhindriyaṃ)? Here, bhikkhus, a noble disciple, having made relinquishment (vossagga) the object, gains concentration (samādhi), gains one-pointedness of mind (citta). This, bhikkhus, is called the faculty of concentration.

English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.

This passage also appears in 1 other place

Vol. 19 · Section 874 — Mudutavagga