Bg 2.68

tasmad yasya maha-baho
nigrhitani sarvasah
indriyanindriyarthebhyas
tasya prajña pratisthita

Word for word: 
tasmat — therefore; yasya — whose; maha-baho — O mighty-armed one; nigrhitani — so curbed down; sarvasah — all around; indriyani — the senses; indriya-arthebhyah — from sense objects; tasya — his; prajña — intelligence; pratisthita — fixed.

Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Therefore, O mighty-armed, one whose senses are restrained from their objects is certainly of steady intelligence.

Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
One can curb the forces of sense gratification only by means of Krishnaconsciousness, or engaging all the senses in the transcendental loving service of the Lord. As enemies are curbed by superior force, the senses can similarly be curbed, not by any human endeavor, but only by keeping them engaged in the service of the Lord. One who has understood this – that only by Krishnaconsciousness is one really established in intelligence and that one should practice this art under the guidance of a bona fide spiritual master – is called a sadhaka, or a suitable candidate for liberation.