“Of all the knowledge that we can ever obtain, the knowledge of God, and the knowledge of ourselves, are the most important.”

Pearls of Wisdom

Introduction
Popular Astronomy: A Series of Lectures Delivered at Ipswich (1868)

Universities, Actual and Ideal (1874)
1870s
Context: In an ideal University, as I conceive it, a man should be able to obtain instruction in all forms of knowledge, and discipline in the use of all the methods by which knowledge is obtained. In such a University, the force of living example should fire the student with a noble ambition to emulate the learning of learned men, and to follow in the footsteps of the explorers of new fields of knowledge. And the very air he breathes should be charged with that enthusiasm for truth, that fanaticism of veracity, which is a greater possession than much learning; a nobler gift than the power of increasing knowledge; by so much greater and nobler than these, as the moral nature of man is greater than the intellectual; for veracity is the heart of morality.

Attributed in posthumous publications, Einstein and Religion (1999)
Context: It seems to me that the idea of a personal God is an anthropomorphic concept which I cannot take seriously. I feel also not able to imagine some will or goal outside the human sphere. My views are near to those of Spinoza: admiration for the beauty of and belief in the logical simplicity of the order and harmony which we can grasp humbly and only imperfectly. I believe that we have to content ourselves with our imperfect knowledge and understanding and treat values and moral obligations as a purely human problem—the most important of all human problems.

From a letter to Murray W. Gross (26 April 1947), p. 138

Source: Guide for the Perplexed (c. 1190), Part III, Ch.23
Context: The words of God are justified, as I will show, by the fact that Job abandoned his first very erroneous opinion, and himself proved that it was an error. It is the opinion which suggests itself as plausible at first thought, especially in the minds of those who meet with mishap, well knowing that they have not merited them through sins. This is admitted by all, and therefore this opinion was assigned to Job. But he is represented to hold this view only so long as he was without wisdom, and knew God only by tradition, in the same manner as religious people generally know Him. As soon as he had acquired a true knowledge of God, he confessed that there is undoubtedly true felicity in the knowledge of God; it is attained by all who acquire that knowledge, and no earthly trouble can disturb it. So long as Job's knowledge of God was based on tradition and communication, and not on research, he believed that such imaginary good as is possessed in health, riches, and children, was the utmost that men can attain; this was the reason why he was in perplexity, and why he uttered the... opinions, and this is also the meaning of his words: "I have heard of thee by the hearing of the ear; but now mine eye seeth thee. Wherefore I abhor myself, and repent because of dust and ashes" (xlii. 5, 6); that is to say, he abhorred all that he had desired before, and that he was sorry that he had been in dust and ashes; comp. "and he sat down among the ashes" (ii. 8) On account of this last utterance, which implies true perception, it is said afterwards in reference to him, "for you have not spoken of me the thing that is right, as my servant Job hath."

Source: Think Big: Unleashing Your Potential for Excellence

Preface, Section 1
On the Genealogy of Morality (1887)