The prayers which the Lord accepts are not the chantings of functionaries, the litanies of priests, or the devout tones of a mechanical service; they must be the prayers of saints: in the life, the character, the soul, the sweetness lies — the acceptance comes not unless they be the prayers of saints.
And who are the saints? They are men whom the Lord has made holy by the power of his Spirit, whose nature he has purified, whom he has washed in the precious blood of Jesus, and so sanctified unto himself, whom he has filled with his Spirit, and so set apart to his worship. These persons loving him, praising him, bowing before him with solemn awe, lifting their whole Souls up in adoring love — these are they who can offer sweet incense; their thoughts, their desires, their longings, their confessions, their pleadings, their praises — these are sweet to God: this is music to him, this is perfume to his heart, delightful to his infinite mind, pleasant to his sacred spirit, for God is a Spirit, and they that worship him must worship him in spirit and in truth, and after no other fashion is a spiritual God to be worshipped.
From a sermon by Charles Haddon Spurgeon entitled "Golden Vials Full of Odors," delivered May 19, 1872.