We say ordinarily that eternity is felt in an instant. What do we mean by that?
When all possibility of measuring a pleasure or an experience by a criterion is gone, when all feeling of necessity and compulsion is gone, when even the duality of the 'now' moment and the one who experiences the 'now' is gone, that is the instant into which eternity empties itself and by which it justifies itself. The' now ' is not a moving phenomenon. It is the look of the subject by which it entices the object and annexes it into it bosom. And when the object is annexed then the attention remains without object. The thought is at its meridian, it measures its own limits, enjoys its own plenitude. It is the all inclusive unifying experience of the witness.
In the Hindu tradition, in addition to the doctrine of Jivanmukti (liberation in the body) there is the notion of immediate release or Sadyomukti, on which Sri Ramakrishna lay much emphasis. The Bhagavadgita says that the moment knowledge comes, one is released.
The Bhagavata puts it beautifully:
'When men realize Me (The Lord)' as present in all beings, as the latent fire is in wood that moment they are liberated of confusion.' So then it is knowledge of this already accomplished identity that releases us immediately. We are in everything. Only this has to be realized and confirmed.
All philosophy and philosophers were attracted by the experience of the eternity in the now-moment. But the first in the Western tradition to give it spirituality was Meister Eckhart : To say that God created the world yesterday or tomorrow would be foolishness, for God created the world and everything in it in the one present Now. Indeed, time that has been past for a thousand years is a present and near to God as the time that now is. The soul that lives in the present Now-moment is the soul in which the Father begets his only begotten Son and in that birth the soul is born again.'
....These were from the article by Swami Nityabodhananda in Vedant Kesari