Ramakrishna’s illness showed no signs of abating in spite of the best available care and treatment. When Narendra realized that the Master would not live long, he intensified his own spiritual practices. One day he entreated Ramakrishna for the experience of nirvikalpa samadhi, the highest realization of Advaita Vedanta. But the Master reprimanded him: “Shame on you! You are asking for such an insignificant thing. I thought that you would be like a big banyan tree, and that thousands of people would rest in your shade. But now I see that you are seeking your own liberation.” He said further: “There is a state higher than that. It is you who sing, ‘O Lord, Thou art all that exists.’” The Master wanted his disciple to see God in all beings and to serve them in a spirit of worship.
One evening, however, when Narendra was meditating with one of his brother disciples at Cossipore, he suddenly became aware of a light at the back of his head, as if a lamp had been placed there. It gradually became more brilliant until finally it seemed to burst. He was engulfed by that light and lost body consciousness. After some time, he began to regain normal consciousness and cried out, “Where is my body?” His amazed brother disciple assured him: “It is here. Don’t you feel it?” He then rushed to the Master’s room upstairs and told him of Narendra’s condition. “Let him stay in that state for a while,” remarked the Master, “he pestered me long enough for it.” For a long time Narendra remained immersed in samadhi, forgetting space, time, and causation. After regaining normal consciousness, he entered the Master’s room, and Ramakrishna told him: “Now the Mother has shown you everything. But this realization, like the jewel locked in a box, will be hidden away from you and kept in my custody. I will keep the key with me. Only after you have fulfilled your mission on this earth will the box be unlocked, and you will know everything as you have known now.” (Source: God Lived with Them)