If we practice Krishna consciousness in this present body while in a healthy condition and in good mind, simply by chanting the holy maha-mantra, Hare Krishna, we will have every possibility of fixing the mind upon Krishna at the time of death. If we do this, then our lives become successful without any doubt. But if we keep our minds always absorbed in fruitive activities for material enjoyment, then naturally at the time of death we shall think of such activities and again be forced to enter material, conditioned bodies to suffer the threefold miseries of material existence.
His Divine Grace A. C. Bhaktivedanta Swami Prabhupada
Krishna, the Supreme Personality of Godhead, Chapter 46

The scripture is revealed transcendental sound that has been visualized in the form of writing. We can hear the transcendental sound vibrations through writings, vibrations that were made by sadhus thousands of years ago. Therefore the shastra, the work of saintly persons, is the deity form of transcendental sound vibration.
Srila Bhaktisiddhanta Sarasvati Thakura
Amrita Vani, “Deity,” No. 5

The body of Sri Krishna is eternal, full of knowledge and bliss. There is no difference between His body and His soul, unlike ordinary embodied beings. On the platform of advaya-jnana, or nondual knowledge, the body is the self and the self is the body. Although the form of Krishna is situated in one place, it is all-pervading.
Srila Bhaktivinoda Thakura
Commentary on Sri Manah-shiksha

The original nature of every living entity is to consider himself the eternal servant of Krishna. But under the influence of maya he thinks himself to be the body, and thus his original consciousness is covered.
Sri Chaitanya Mahaprabhu
Sri Chaitanya-charitamrita, Madhya-lila 24.201

It is the duty of every conditioned soul to engage his polluted consciousness, which is now attached to material enjoyment, in very serious devotional service with detachment. Thus his mind and consciousness will be under full control.
Lord Kapila
Srimad-Bhagavatam 3.27.5

My dear daughter of Garga, His greatness encompasses everything above us in heaven, everything below the surface of the earth, everything in between heaven and earth, and everything that has ever existed, exists now, or will ever exist.
Brihad-aranyaka Upanishad 3.8.4

Therefore Krishna is the Supreme Godhead. One should meditate on Him, relish the taste of reciprocating loving exchanges with Him, worship Him and offer sacrifice to Him.
Gopala-tapani Upanishad, Purva 50