One should first recognize the Buddha-Nature, then train in it, and finally attain stability. In order to recognize the Buddha-Nature, we must identify exactly what is preventing us from realizing it now and what needs to be cleared away - all the passing stains of confusion. Where did these passing stains come from ? The ground itself, the Buddha-Nature, is without impurity or confusion, but the temporary defilements, the stains of confusion, result from not having recognized the state of the ground.
What is fruition ? The immaculate Dharmakaya is the fruition of having purified these stains. Through practice, we unveil a state free from all dualistic phenomena, free from holding on to subject and object, perceiver and perceived. Having totally discarded all the different ways of being mistaken, having rid oneself of the passing stains, we realize Dharmakaya, the ground itself exactly as it is. This is the fruition of purification.

~ Chokyi Nyima Rinpoche