Preachers often pray for unction as they preach, but what is it? E.M. Bounds explains:
Unction is that indefinable, indescribable something which an old, renowned Scotch preacher describes thus: ‘There is sometimes somewhat in preaching that cannot be described either be matter of expression, and cannot be described what it is, or from whence it cometh, but with a sweet violence it pierceth into the heart and affections and comes immediately from the Lord.’ We call it unction. It is this unction which makes the Word of God ‘quick and powerful, and sharper than any two-edged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and a discerner of the thoughts and intents of the heart.’ It is this unction which gives the words of the preacher such point, sharpness, and power, and which creates such friction and stir in many a dead congregation. The same truths have been told in the strictness of the letter, smooth as human oil could make them; but no signs of life, not a pulse throb; all as peaceful as the grave and as dead. The same preacher in the meanwhile receives a baptism of this unction, the divine inflatus is on him, the letter of the Word has been embellished and fired by this mysterious power, and the throbbing of life begin – life which receives or life which resists. The unction pervades and convicts the conscience and breaks the heart.
This divine unction is the feature which separates and distinguishes true gospel preaching from all other methods of presenting the turret, and which creates a wide spiritual chasm between the preacher who has it and the one who has it not. It supports and impregnates revealed truth with all the energy of God. Unction is simply putting God in his own Word and on his own preacher. By mighty and great prayerfulness and by continual prayerfulness, it is all potential and personal to the preacher; it inspires and clarifies his intellect, gives insight and grasp and projecting power; it gives to the preacher heart power, which is greater than head power; and tenderness, purity, force flow from the heart by it. Enlargement, freedom, fullness of thought, directness and simplicity of utterance are the fruits of this unction… what of unction? It is the indefinable in preaching which makes it preaching. It is that which distinguishes and separates preaching from all mere human addresses. It is the divine in preaching.
E.M. Bounds in Power Through Prayer (Chapter 15)
(By: Nick Kennicott)