Osho relates a story attributed to St. Augustine of Hippo (354 – 430 CE). The answer is: “Just love.”
Somebody asked Augustine of Hippo:
”I am a very uneducated man and I cannot read scriptures and great theology books. You just give me a small message. I’m very foolish and my memory is also not good, so you just give me a gist, so I can remember it and follow it.”
Augustine was a great philosopher, a great saint, and he had delivered great sermons, but nobody had asked for just a gist. He closed his eyes, he meditated for hours, it is said.
And the man said, ”Please, if you have found, just tell me so I can go, because I have been waiting for hours.”
Augustine said, ”I cannot find anything else except this: love, and everything else is permitted to you. Just love.”
Osho, Yoga: The Alpha and the Omega – Discourses on the Yoga Sutras of Patanjali, Vol 10, Ch 10, Q 4 (excerpt)