Peace and purity of the consciousness are the very foundation of the necessary change in the nature.

Peace is necessary for all; without peace and an increasing purity, even if one opens, one cannot receive perfectly all that comes down through the opening. Light too is necessary for all—without light one cannot take full advantage of all that comes down.

Peace is necessary for the higher states to develop.

Equanimity and peace in all conditions in all parts of the being is the first foundation of the Yogic status. Either Light (bringing with it knowledge) or Force (bringing strength and dynamism of many kinds) or Ananda (bringing love and joy of existence) can come next according to the trend of the nature. But peace is the first condition without which nothing else can be stable.

The first thing that you have to bring down is a positive, complete and enduring peace from above—that is the only foundation on which the rest can be done, i.e. the development of the higher consciousness, force, knowledge, love, Ananda.

Ref : Letters on Yoga Vol. II