The third sort of prayer is only in the heart without speech, with great rest and quietness both of soul and body. A pure heart it behoveth him to have that shall pray after this manner; for such only attain to it who by long travail both of body and soul, or else by such sharp touches or motions of love, as I have before mentioned, have arrived to rest of spirit, so that his affections are turned into spiritual savour and relish, that he is able to pray continually in his heart, and love and praise God without great letting of temptations or of vanities, as is said before in the chapter of the second sort of Contemplation. (John Climacus)

The heart seems to overflow.

In peaceful contemplation, with gradual increasing insight,

When suddenly the heart will flood with thanksgiving and praise,

And for hours or even days the flood does continue,

Sweeping away all that is not a gift of God.