vedāhaḿ samatītāni
vartamānāni cārjuna
bhaviṣyāṇi ca bhūtāni
māḿ tu veda na kaścana

Translation of Bhagavad Gita 7.26

O Arjuna, as the Supreme Personality of Godhead, I know everything that has happened in the past, all that is happening in the present, and all things that are yet to come. I also know all living entities; but Me no one knows.

Commentary by Sri A.C. Bhaktivedanta Swami Prabhupada of Gaudiya Sampradaya:

Here the question of personality and impersonality is clearly stated. If Krishna, the form of the Supreme Personality of Godhead, were maya, material, as the impersonalists consider Him to be, then like the living entity He would change His body and forget everything about His past life. Anyone with a material body cannot remember his past life, nor can he foretell his future life, nor can he predict the outcome of his present life; therefore he cannot know what is happening in past, present and future. Unless one is liberated from material contamination, he cannot know past, present and future.

Unlike the ordinary human being, Lord Krishna clearly says that He completely knows what happened in the past, what is happening in the present, and what will happen in the future. In the Fourth Chapter we have seen that Lord Krishna remembers instructing Vivasvan, the sun-god, millions of years ago. Krishna knows every living entity because He is situated in every living being’s heart as the Supersoul. But despite His presence in every living entity as Supersoul and His presence as the Supreme Personality of Godhead, the less intelligent, even if able to realize the impersonal Brahman, cannot realize Sri Krishna as the Supreme Person. Certainly the transcendental body of Sri Krishna is not perishable. He is just like the sun, and maya is like a cloud. In the material world we can see that there is the sun and that there are clouds and different stars and planets. The clouds may cover all these in the sky temporarily, but this covering is only apparent to our limited vision. The sun, moon and stars are not actually covered. Similarly, maya cannot cover the Supreme Lord. By His internal potency He is not manifest to the less intelligent class of men. As it is stated in the third verse of this chapter, out of millions and millions of men, some try to become perfect in this human form of life, and out of thousands and thousands of such perfected men, hardly one can understand what Lord Krishna is. Even if one is perfected by realization of impersonal Brahman or localized Paramatma, he cannot possibly understand the Supreme Personality of Godhead, Sri Krishna, without being in Krishna consciousness.

Commentary by Sri Vishvanatha Chakravarthi Thakur of Gaudiya Sampradaya:

But my knowledge is not covered by external maya or the internal yogamaya, since I cannot be bewildered by that to which I give shelter. I know everything. But no one, whether material or spiritual,  even Siva, most omniscient person,  knows me completely, since knowledge of me is covered by either maya or yogamaya according to the qualification of the person.

Commentary by Sri Ramanuja of Sri Sampradaya:

7.26 I know all being that have passed away, those that live now and those that will hereafter. But no one knows Me. Among the beings existing in the three-fold divisions of time whom I look after, no one understands Me as of the nature described and as Vasudeva incarnated to be a refuge for all. So no one resorts to Me. Therefore, the one who knows Me really (Jnanin) is extremely difficult to be found. Such is the meaning. So also:

Commentary by Sri Sridhara Swami of Rudra Sampradaya:

Lord Krishna has previously stated that the ignorant are oblivious about His supreme nature. Now He reveals that a part of His nature consists of omniscience. He confirms that He knows all beings movable and immovable in their present existence, all those that perished in their past existence and the future lives of all those that are yet to come into existence. His external energy known as maya is illusory impressions superimposed upon the mind which deludes all living entities; but as He is the foundation of maya He alone can never be deluded for maya is subservient and dependent upon Him.

Commentary by Sri Madhvacharya of Brahma Sampradaya:

Lord Krishna explains that for Him there is never any illusion; but the embodied beings without His grace emanating through the bonafide spiritual master in authorised disciplic succession will find it impossible to extricate themselves from maya or illusory impressions superimposed upon the mind. It should be clearly understood that no one can know Lord Krishna by their own efforts regardless how great. He is only known by His own desire.

Now begins the summation.

As much as Lord Krishna is known to Himself none other can know Him. Brahma the demigod responsible for material creation and Shiva the demigod responsible for material destruction, by His grace know Him partially to some extent according to their ability and gradation. The Katha Upanisad I.II.XXIII is categorical in its declaration that: The Supreme Lord cannot be attained by instruction or by intelligence or even by constant hearing about. Whom the Supreme Lord Himself chooses, only is able to attain Him and none other. Only to the one He chooses doe He reveal His rupa form, guna or qualities and lila His phenomenal pastimes.

Commentary by Sri Keshava Kashmiri of Kumara Sampradaya:

Lord Krishna emphasises by the words mam tu veda na kascam which means that no one is able to know Him and because He is the controller of all, anywhere that He is not veiled is only by His express directive for His veiling is not for His devotees but for those who are in the clutches of maya or illusory impressions superimposed upon the mind, so that they will not be able to know Him. This He is indicating by the word vedaham meaning He knows. That He knows by His divine potency and unveiled knowledge. Although His external energy known as maya veils the mind in varying degrees of all created beings; it should clearly understood that that all living beings movable or immovable, belonging to the past, existing in the present or manifesting in the future are under His complete control and this is an example of how He is omniscient. It should also be clearly understood that no one bereft of devotion to the Supreme lord due to being bewildered and under the control of maya has the qualification to know that Lord Krishna is the Supreme Lord within their heart and within the heart of every living entity being present everywhere. Hence such ignorant living entities do not become devoted to Him.

Commentary by Sri Adi Shankaracharya of Advaita Sampradaya:

7.26 O Arjuna, aham, I, however; veda, know; samatitani, the past beings; and vartamanani, the present. I know ca, also; bhavisyani, the future; bhutani, beings. Tu, but; na kascana, no one; veda, knows; mam, Me. Except the one person who is My devotee and has taken refuge in Me, no one adores Me, jus because he does not know My reality. ‘What, again,is the obstruction to knowing Your reality, being prevented by which the creatures that are born do not know You?’ In anticipation of such a question, the Lord says this:

Commentary by Sri Abhinavagupta of Kaula Tantra Sampradaya:

7.25-26 Naham etc. Vadaham etc. I am not perceivable to all. But the actions themselves, if performed, would beget emancipation at the time of dissolution [of the world]. otherwise, how does the total dissolution come to be there ? When this doubt arises, [the Bhagavat] commences [to answer] as :

Sanskrit Shloka Without Transliteration Marks:

vedaham samatitani
vartamanani carjuna
bhavisyani ca bhutani
mam tu veda na kascana

Sanskrit to English Word for Word Meanings:

veda — know; aham — I; samatītāni — completely past; vartamānāni — present; ca — and; arjuna — O Arjuna; bhaviṣyāṇi — future; ca — also; bhūtāni — all living entities; mām — Me; tu — but; veda — knows; na — not; kaścana — anyone.