In Matthew 22:37 A student of the law came to Jesus and asked him a question, tempting him, and saying,
Master, which is the great commandment in the law?
Jesus said to him, ‘You shall love the LORD your God with all your heart, with all your soul, and with all your mind.’ This is the first and great commandment. 
Jesus was quoting what is known in Hebrew as the Shema (Hear).
Shema is pulled from Deuteronomy chapter 6 of the Torah, the first five books of the Bible.  It is the oldest fixed daily prayer in Judaism, recited morning and night since before the time of Christ.

In September 1942, Jewish psychiatrist Victor Frankl was arrested by the Nazis during World War II, everything of value was killed or destroyed: property, family, his pregnant wife, Tilly, his possessions, everything.
When he arrived in Auschwitz, the infamous death camp, even his most treasured manuscripts, which he had hidden in the lining of his coat, was taken away.
“I had to surrender my clothes and in turn inherited the worn-out rags of an inmate who had been sent to the gas chamber,” said Frankl. “Instead of the many pages of my manuscript, I found in the pocket of the newly acquired coat a single page torn out of a Hebrew prayer book, which contained the main Jewish prayer, SHEMA YISRAEL (Hear, O Israel! The Lord our God is one God. And you shall love the Lord your God with all your heart and with all your soul and with all your might.)
“How should I have interpreted such a ‘coincidence’ other than as a challenge to LIVE my thoughts instead of merely putting them on paper?”
After the lose of his manuscripts he writes: “I had to undergo and overcome the loss of my spiritual child, “ Frankl wrote. “Now it seemed as if nothing and no one would survive me; neither a physical nor a spiritual child of my own! I found myself confronted with the question of whether under such circumstances my life was ultimately void of any meaning.”
He recalls the first days at Auschwitz:
“We stumbled on in the darkness, over big stones and through large puddles, along the one road leading from the camp. The accompanying guards kept shouting at us and driving us with the butts of their rifles. Anyone with very sore feet supported himself on his neighbor’s arm. Hardly a word was spoken; the icy wind did not encourage talk. Hiding his mouth behind his upturned collar, the man marching next to me whispered suddenly: “If our wives could see us now! I do hope they are better off in their camps and don’t know what is happening to us.”
That brought thoughts of my own wife to mind. And as we stumbled on for miles, slipping on icy spots, supporting each other time and again, dragging one another up and onward, nothing was said, but we both knew: each of us was thinking of his wife. Occasionally I looked at the sky, where the stars were fading and the pink light of the morning was beginning to spread behind a dark bank of clouds. But my mind clung to my wife’s image, imagining it with an uncanny acuteness. I heard her answering me, saw her smile, her frank and encouraging look. Real or not, her look was then more luminous than the sun which was beginning to rise.
Before the war, he had bought his wife a pendant, a small golden globe with blue enamel oceans. On a gold band wrapping around the globe were engraved the words, “The whole world turns on love.” As Frankl marched, the sun began to rise, and it dawned in him how, “Love goes very far beyond the physical person of the beloved. It finds its deepest meaning in his spiritual being, his inner self.”
A thought transfixed me: for the first time in my life I saw the truth as it is set into song by so many poets, proclaimed as the final wisdom by so many thinkers. The truth — that love is the ultimate and the highest goal to which man can aspire. Then I grasped the meaning of the greatest secret that human poetry and human thought and belief have to impart: The salvation of man is through love and in love.
I understood how a man who has nothing left in this world still may know bliss, be it only for a brief moment, in the contemplation of his beloved. In a position of utter desolation, when man cannot express himself in positive action, when his only achievement may consist in enduring his sufferings in the right way — an honorable way — in such a position man can, through loving contemplation of the image he carries of his beloved, achieve fulfillment.”
Later, as Frankl reflected on his ordeal, in his book MAN’S SEARCH FOR MEANING, he writes: ‘There is nothing in the world that would so effectively help one to survive even the worst conditions, as the knowledge that there is a meaning in one’s life…He who has a WHY to live for can bear almost any HOW.’”
And Jesus said, ‘You shall love the LORD your God with all your heart, with all your soul, and with all your mind.’ This is the first and great commandment.