Charles H. Spurgeon on Psalms 141:2

Let my prayer be set forth before thee as incense. As incense is carefully prepared, kindled with holy fire, and devoutly presented unto God, so let my prayer be. We are not to look upon prayer as easy work requiring no thought. It needs to be "set forth"; what is more, it must be set forth "before the Lord, "by a sense of his presence and a holy reverence for his name: neither may we regard all supplication as certain of divine acceptance, it needs to be set forth before the Lord "as incense, "concerning the offering of which there were rules to be observed, otherwise it would be rejected of God. And the lifting up of my hands as the evening sacrifice. Whatever form his prayer might take his one desire was that it might be accepted of God. Prayer is sometimes presented without words by the very motions of our bodies: bent knees and lifted hands are the tokens of earnest, expectant prayer. Certainly work, or the lifting up of the hands in labour, is prayer if it be done in dependence upon God and for his glory: there is a hand prayer as well as a heart prayer, and our desire is that tiffs may be sweet unto the Lord as the sacrifice of eventide. Holy hope, the lifting up of hands that hang down, is also a kind of worship: may it ever be acceptable with God. The Psalmist makes a bold request: he would have his humble cries and prayers to be as much regarded of the Lord as the appointed morning and evening sacrifices of the holy place. Yet the prayer is by no means too bold, for, after all, the spiritual is in the Lord's esteem higher than the ceremonial, and the calves of the lips are a truer sacrifice than the calves of the stall. So far we have a prayer about prayer: we have a distinct supplication in the two following verses.