BG 6.12-13

Seated firmly on it, the yogi should strive to purify the mind by focusing it in meditation with one pointed concentration, controlling all thoughts and activities. He must hold the body, neck, and head firmly in a straight line, and gaze at the tip of the nose, without allowing the eyes to wander.

BG 7.21

Whatever celestial form a devotee seeks to worship with faith, I steady the faith of such a devotee in that form.

BG 12.3-4

But those who worship the formless aspect of the Absolute Truth—the imperishable, the indefinable, the unmanifest, the all-pervading, the unthinkable, the unchanging, the eternal, and the immoveable—by restraining their senses and being even-minded everywhere, such persons, engaged in the welfare of all beings, also attain Me.