Chapter 6 · The Yoga of Meditation · Krishna said
Bhagavad Gita 6.12 — One-pointed mind
तत्रैकाग्रं मनः कृत्वा यतचित्तेन्द्रियक्रियः। उपविश्यासने युञ्ज्याद्योगमात्मविशुद्धये ॥
tatraikāgraṃ manaḥ kṛtvā yatacittendriyakriyaḥ | upaviśyāsane yuñjyādyogamātmaviśuddhaye ||
Meaning
Sitting on that seat, making the mind one-pointed and controlling the workings of mind and senses, he should practise yoga to purify himself.