The entire process of withdrawing consciousness from the universe and becoming conscious of the Self is accompanied by an increasing control of all the vehicles of consciousness. Such control is made possible by the vivification and activation of unused centers of control, and the functioning of new centers brings in its train a number of hidden powers. These new powers are commonly known as siddhis, and they can come before the aspirant has become spiritually perfect. In fact, egotism can flourish through the acquisition of such powers. The aspirant may not only take delight in possessing them but might actually use them for mundane purposes from which he has not necessarily freed himself.
Siddhis are therefore rightly regarded as obstacles to the attainment of Realization. However, after God is realized all these powers dwindle in their importance. The siddhis have their scope in the nothingness that is the universe; whereas the person who realizes God is permanently and immovably established in the supreme Reality. Although the whole universe is like a zero to the God-realized person, he may voluntarily assume responsibility for those souls who are enmeshed in the tangles of the universe. In that case he can freely and legitimately make use of these powers for the spiritual good of others.
-Discourses 7th Ed., p 191