Charles H. Spurgeon on Psalms 27:6

And now shall mine head be lifted up above mine enemies round about me. He is quite sure of it. Godly men of old prayed in faith, nothing wavering, and spoke of their answer to their prayers as a certainty. David was by faith so sure of a glorious victory over all those who beset him, that he arranged in his own heart what he would do when his foes lay all prostrate before him; that arrangement was such as gratitude suggested. Therefore will I offer in his tabernacle sacrifices of joy. That place for which he longed in his conflict, should see his thankful joy in his triumphant return. He does not speak of jubilations to be offered in his palace, and feastings in his banqueting halls, but holy mirth he selects as most fitting for so divine a deliverance. I will sing. This is the most natural mode of expressing thankfulness. Yea, I will sing praises unto the Lord. The vow is confirmed by repetition, and explained by addition, which addition vows all the praise unto Jehovah. Let who will be silent, the believer when his prayer is heard, must and will make his praise to be heard also; and let who will sing unto the vanities of the world, the believer reserves his music for the Lord alone.