Here is a Spurgeon quote from my sermon on Psalm 100:
“Those who serve God with a sad countenance, because they do what is unpleasant to them, are not serving him at all; they bring the form of homage, but the life is absent. Our God requires no slaves to grace his throne; he is the Lord of the empire of love, and would have his servants dressed in the uniform of joy. The angels of God serve him with songs, not with groans; a murmur or a sigh would be a mutiny in their ranks. That obedience which is not voluntary is disobedience, for the Lord looketh at the heart, and if he seeth that we serve him from force, and not because we love him, he will reject our offering.
Let us show to the people of the world, who think our religion to be slavery, that it is to us a delight and a joy! Let our gladness proclaim that we serve a good Master.”